Control Of Parallel Multiple Converters For Direct-Drive Permanent-Magnet Wind Power Generation Systems

Control Of Parallel Multiple Converters For Direct-Drive Permanent-Magnet Wind Power Generation Systems

ABSTRACT:

This paper proposes control strategies for mega watt level direct-drive wind generation systems based on permanent magnet synchronous generators. In the paper, a circulating current model is derived and analyzed. The parallel-operation controllers are designed to restrain reactive power circulation and beat frequency circulation currents caused by discontinuous space vector modulation. The control schemes do not change the configurations of the system consisting of parallel multiple converters. They are easy to implement for modular designs and large impedance required to equalize the current sharing is not needed. To increase the system reliability, a robust adaptive sliding observer is designed to sense the rotor position of the wind power generator. The experimental results proved the effectiveness of the control strategies.

KEYWORDS:

1.      Circulation currents

2.       Parallel multiple converters

3.       Permanent magnet synchronous generators (PMSGs)

4.      Wind power

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. High-Power Direct-Drive PMSG Wind Generator System Connected To The Power Grid.

CONCLUSION:

This paper has comprehensively addressed the control issues of parallel three-phase PWM converters for the permanent magnet wind power generation systems. The major accomplishments and some conclusions are summarized in the following.

1) A peak current model of zero-sequence currents has been derived and analyzed for the three-phase PWM converters in parallel connection.

2) A zero-sequence current control scheme has been adapted to reject the zero-sequence current inside an individual converter.

3) An adaptive observer has been integrated with parallel operation control experimentally. The performance of position sensorless control of the generator has been greatly enhanced and the reliability has been increased.

4) Zero-sequence currents have been successfully suppressed for the back-to-back converters with parallel connection. Large impedance needed to equalize the current sharing has been removed.

5) Experimental verification of the control of the three-phase PWM converters in parallel confirms the good performance and promising features of the proposed directly driven permanent magnet synchronous power generation system.

REFERENCES:

[1] T. Kawabata And S. Higashino, “Parallel Operation Of Voltage Source Inverters,” Ieee Trans. Ind. Appl., Vol. 24, No. 2, Pp. 281–287, Mar./Apr. 1988.

[2] J. Holtz, W. Lotzkat, And K. H. Werner, “A High-Power Multi-Transistorinverter Uninterruptable Power Supply System,” Ieee Trans. Power Electron., Vol. 3, No. 3, Pp. 278–285, Jul. 1988.

[3] L. H.Walker, “10mwgto Converter For Battery Peaking Service,” Ieee Trans. Ind. Appl., Vol. 26, No. 1, Pp. 63–72, Jan./Feb. 1990.

[4] S. Fukuda And K. Matsushita, “A Control Method For Parallel-Connected Multiple Inverter Systems,” Presented At The 7th Int. Conf. Power Electron. Variable Speed Drives, London, U.K., 1998.

[5] X. Kun, F. C. Lee, D. Boroyevich, Y. Zhihong, And S. Mazumder, “Interleaved Pwm With Discontinuous Space-Vector Modulation,” Ieee Trans. Power Electron., Vol. 14, No. 5, Pp. 906–917, Sep. 1999.

A Novel Online Fuzzy Control Method of Static VAR Compensation for an Effective Reactive Power Control of Transmission Lines

A Novel Online Fuzzy Control Method of Static VAR Compensation for an Effective Reactive Power Control of Transmission Lines

ABSTRACT:

The Flexible AC Transmission System (FACTS) technology is a promising technology to achieve complete deregulation of Power System i.e. Generation, Transmission and Distribution as the complete individual units. FACTS is based on power electronic devices, used to enhance the existing transmission capabilities in order to make the transmission system flexible and independent in operation. The loading capability of transmission system can also be enhanced nearer to its thermal limit without affecting the stability. Complete closed-loop smooth control of reactive power can be achieved using shunt connected FACTS devices. Static VAR Compensator (SVC) is one of the shunt connected FACTS devices, which can be utilized for the purpose of reactive power compensation. As the Intelligent FACTS devices make them adaptable, it is emerging as the present state of the art technology. This paper presents the design and simulation of the Fuzzy logic control to vary firing angle of SVC in order to achieve better, smooth and adaptive control of reactive power in transmission systems. The design, modeling and simulations are carried out for the λ/8 Transmission line by placing the compensation at the receiving end (load end) and the results obtained demonstrates the effectiveness of the proposed method.

KEYWORDS:

1.      Fuzzy Logic

2.       FACTS and SVC

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

      

Fig. 1.Structure of fuzzy logic controller..

Fig.2. Single Phase equivalent circuit and fuzzy logic control structure of SVC.

 CONCLUSION:

This paper presents an “online Fuzzy control scheme for SVC” and it can be concluded that the use of fuzzy controlled SVC (FC-TCR) compensating device with the firing angle control is continuous, effective and it is a simplest way of controlling the reactive power of transmission line. It is observed that  SVC device was able to compensate both over and under voltages. Compensated voltages are shown in Fig. 17 and Fig. 18. The use of fuzzy logic has facilitated the closed loop control of system, by designing a set of rules, which decides the firing angle given to SVC to attain the required voltage. With MATLAB simulations [4] [5] and actual testing it is observed that SVC (FC-TCR) provides an effective reactive power control irrespective of the load variations.

REFERENCES:

1.     Narain. G. Hingorani, “Understanding FACTS, Concepts and Technology Of flexible AC Transmission Systems”, by IEEE Press USA.

2.     Bart Kosko, “Neural Networks and Fuzzy Systems A Dynamical Systems Approach to Machine Intelligence”, Prentice-Hall of India New Delhi, June 1994.

3.     Timothy J Ross, “Fuzzy Logic with Engineering Applications”, McGraw-Hill, Inc, New York, 1997.

4.     Laboratory Manual for Transmission line and fuzzy Trainer Kit Of Electrical  Engineering Department NIT Warangal.

5.   SIM Power System User Guide Version 4 MATLAB Manual

Multi converter Unified Power-Quality Conditioning System: MC-UPQC

Multi converter Unified Power-Quality Conditioning System: MC-UPQC

ABSTRACT:

This paper presents a new unified power-quality conditioning system (MC-UPQC), capable of simultaneous compensation for voltage and current in multi bus/multi feeder systems. In this configuration, one shunt voltage-source converter (shunt VSC) and two or more series VSCs exist. The system can be applied to adjacent feeders to compensate for supply-voltage and load current imperfections on the main feeder and full compensation of supply voltage imperfections on the other feeders. In the proposed configuration, all converters are connected back to back on the dc side and share a common dc-link capacitor. Therefore, power can be transferred from one feeder to adjacent feeders to compensate for sag/swell and interruption. The performance of the MC-UPQC as well as the adopted control algorithm is illustrated by simulation. The results obtained in PSCAD/EMTDC on a two-bus/two-feeder system show the effectiveness of the proposed configuration.

KEYWORDS:

1.      Power quality (PQ)

2.       PSCAD/EMTDC

3.       Unified power-quality conditioner (UPQC)

4.       voltage-source converter (VSC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Typical MC-UPQC used in a distribution system.

Fig.2. Control block diagram of the shunt VSC.

Fig.3. Control block diagram of the series VSC.

CONCLUSION:

In this paper, a new configuration for simultaneous compensation of voltage and current in adjacent feeders has been proposed. The new configuration is named multi converter unified power-quality conditioner (MC-UPQC). Compared to a conventional UPQC, the proposed topology is capable of fully protecting critical and sensitive loads against distortions, sags/swell, and interruption in two-feeder systems. The idea can be theoretically extended to multi bus/multi feeder systems by adding more series VSCs. The performance of the MC-UPQC is evaluated under various disturbance conditions and it is shown that the proposed MC-UPQC offers the following advantages:

1) power transfer between two adjacent feeders for sag/swell and interruption compensation;

2) compensation for interruptions without the need for a battery storage system and, consequently, without storage capacity limitation;

3) sharing power compensation capabilities between two adjacent feeders which are not connected.

REFERENCES:

 [1] D. D. Sabin and A. Sundaram, “Quality enhances reliability,” IEEE Spectr., vol. 33, no. 2, pp. 34–41, Feb. 1996.

[2] M. Rastogi, R. Naik, and N. Mohan, “A comparative evaluation of harmonic reduction techniques in three-phase utility interface of power electronic loads,” IEEE Trans. Ind. Appl., vol. 30, no. 5, pp. 1149–1155, Sep./Oct. 1994.

[3] F. Z. Peng, “Application issues of active power filters,” IEEE Ind. Appl. Mag., vol. 4, no. 5, pp. 21–30, Sep../Oct. 1998.

[4] H. Akagi, “New trends in active filters for power conditioning,” IEEE Trans. Ind. Appl., vol. 32, no. 6, pp. 1312–1322, Nov./Dec. 1996.

[5] L. Gyugyi, C. D. Schauder, S. L. Williams, T. R. Rietman, D. R. Torjerson, 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.

Direct Power Control Of Series Converter Of Unified Power-Flow Controller With Three-Level Neutral Point Clamped Converter

Direct Power Control Of Series Converter Of Unified Power-Flow Controller With Three-Level Neutral Point Clamped Converter

ABSTRACT:

A unified power-flow controller (UPFC) can enforce unnatural power flows in a transmission grid, to maximize the power flow while maintaining stability. Theoretically, active and reactive power flow can be controlled without overshoot or cross coupling. This paper develops direct power control, based on instantaneous power theory, to apply the full potential of the power converter. Simulation and experimental results of a full three-phase model with non ideal transformers, series multilevel converter, and load confirm minimal control delay, no overshoot nor cross coupling. A comparison with other controllers demonstrates better response under balanced and unbalanced conditions. Direct power control is a valuable control technique for a UPFC, and the presented controller can be used with any topology of voltage-source converters. In this paper, the direct power control is demonstrated in detail for a third-level neutral point clamped converter.

KEYWORDS:

1.      Direct power control

2.       Flexible ac transmission control (FACTS)

3.       Multilevel converter

4.       Sliding mode control

5.       Unified power-flow controller (UPFC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1.Laboratory setup.

 CONCLUSION:

The DPC technique was applied to a UPFC to control the power flow on a transmission line. The technique has been described in detail and applied to a three-level NPC converter. The main benefits of the control technique are fast dynamic control behavior with no cross coupling or overshoot, with a simple controller, independent of nodal voltage changes. The realization was demonstrated by simulation and experimental results on a scaled model of a transmission line. The controller was compared to two other controllers under balanced and unbalanced conditions, and demonstrated better performance, with shorter settling times, no overshoot, and indifference to voltage unbalance. We conclude that direct power control is an effective method that can be used with UPFC. It is readily adaptable to other converter types than the three-level converter demonstrated in this paper.

REFERENCES:

 [1] L. Gyugyi, “Unified power-flow control concept for flexible ac transmission systems,” Proc. Inst. Elect. Eng., Gen., Transm. Distrib., vol. 139, no. 4, pp. 323–331, Jul. 1992.

[2] L. Gyugyi, C. Schauder, S.Williams, T. Rietman, D. 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.

[3] X. Lombard and P. Therond, “Control of unified power flow controller: Comparison of methods on the basis of a detailed numerical model,” IEEE Trans. Power Syst., vol. 12, no. 2, pp. 824–830, May 1997.

[4] H. Wang, M. Jazaeri, and Y. Cao, “Operating modes and control interaction analysis of unified power flow controllers,” Proc. Inst. Elect. Eng., Gen., Transm. Distrib., vol. 152, no. 2, pp. 264–270, Mar. 2005.

[5] H. Fujita, H. Akagi, and Y. Watanabe, “Dynamic control and performance of a unified power flow controller for stabilizing an ac transmission system,” IEEE Trans. Power Electron., vol. 21, no. 4, pp. 1013–1020, Jul. 2006.

Speed Control of Separately Excited DC Motor

Speed Control of Separately Excited DC Motor

ABSTRACT:

This paper proposes the speed control of a separately excited dc motor varying armature voltage. The novelty of this paper lies in the application of nonlinear autoregressive-moving average L2 controller for the speed control of SEDM. This paper also discusses speed control of a SEDM using chopper circuit. The performance of the proposed system has been compared with the traditional one using conventional controllers. The entire system has been modeled using MATLAB 7.0 toolbox. It has been found that both PI and hysteresis current controllers could be eliminated by the use of NARMA-L2 controller.

KEYWORDS:

1.      Chopper Circuit

2.       NARMA-L2

3.       SEDM

4.       Speed control

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 Fig. 1: Speed control circuit of a separately excited dc motor

 CONCLUSION:

Speed controller system based on NARMA-L2 controller has been successfully developed using

MATLAB to control the speed of a separately excited dc motor. The novelty of this paper lies in the application of NARMA–L2 controller to control of a separately excited dc motor. This paper also discusses modeling and control of SEDM using Sim Power Systems and simulink models. The performance of the system has been compared using different types of controllers. It has been found that NARMA-L2 controller is able to regulate the speed well above the rated values.

REFERENCES:

1. Zuo Z. Liu, Fang L. Luo, and Muhammad H. Rasid, “High performance nonlinear MIMO field weakening controller of a separately excited dc motor,” Electric Power Systems Research, vol. 55, issue 3, Sep. 2000, pp. 157-164.

2. Nabil A. Ahmed, “Modeling and simulation of acdc buck-boost converter fed dc motor with uniform PWM technique,” Electric Power Systems Research, vol.73, issue 3, Mar. 2005, pp. 363-372.

3. J. Figueroa, C. Brocart, J. Cros, and P. Viarouge, “Simplified simulation methods for polyphase brushless DC motors,” Mathematics and Computers in Simulation, vol. 63, issues 3-5, Nov. 2003, pp. 209-224.

4. J. Santana, J. L. Naredo, F. Sandoval, I. Grout, and O. J. Argueta, “Simulation and construction of a speed control for a DC series motor,” Mechatronics, vol. 12, issues 9-10, Nov.-Dec. 2002, pp. 1145-1156.

5. Charles I. Ume, John Ward, and Jay Amos, “Application of MC68HC11 microcontroller for speed control of a DC motor,” Journal of Microcomputer Applications, vol. 15, issue 4, Oct. 1992, pp. 375-385. 

STATCOM for Improved Dynamic Performance of Wind Farms in Power Grid

              STATCOM for Improved Dynamic Performance of Wind

Farms in Power Grid

ABSTRACT:

Application of FACTS controller called Static Synchronous Compensator STATCOM to improve the performance of power grid with Wind Farms is investigated .The essential feature of the STATCOM is that it has the ability to absorb or inject fastly the reactive power with power grid . Therefore the voltage regulation of the power grid with STATCOM FACTS device is achieved. Moreover restoring the stability of the power system having wind farm after occurring severe disturbance such as faults or wind farm mechanical power variation is obtained with STATCOM controller . The dynamic model of the power system having wind farm controlled by proposed STATCOM is developed . To Validate the powerful of the STATCOM FACTS controller , the studied power system is simulated and subjected to different severe disturbances . The results prove the effectiveness of the proposed STATCOM controller in terms of fast damping the power system oscillations and restoring the power system stability .

KEYWORDS:

1.      STATCOM

2.       Wind Generation

3.       Transient Stability

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Studied model

 CONCLUSION:

Power system with wind farms performance can be improved using FACTS devices such as STATCOM . The dynamic model of the studied power system is simulated using Simulink Matlab package sofware . To validate the effect of the STATCOM controller of power system operation , the system is subjected to different disturbances such as faults and power operating conditions . The digital results prove the powerful of the proposed STATCOM controller in terms of Stability improvement, power swings damping, voltage regulation, increase of power transmission and chiefly as a supplier of controllable reactive power to accelerate voltage recovery after fault occurrence.

 REFERENCES:

 [1] V. Akhmatov, H.knudsen, A.H. Nielsen, J.K.pedersen, and N.K. poulsen, "A dynamic stability limit of grid connected induction generators", Pro. International IASTED conference on power and energy systems, marbella, spain, 2000.

[2] L. holdsworth, X.G. Wu, J.B. EKanayake, and N. Jenkins, "Comparison of fixed-speed and doubly-fed induction generator wind turbines during power system disturbances", IEE proc. C-Gener. Transm. Distrib., vol. 150, no. 3, pp. 343-352, 2003.

[3] S.M. Bolik, "Grid requirments challenges for wind turbines", Fourth International Workshop on large-scale Integration of Wind Power and transmission networks for Offshore Wind Farms, Oct .2003.

[4] L. Holdsworth, N.Jenkins, and G. Strbac, "Electrical stability of large, offshore wind farms", IEE seventh International Conference on AC-DC power Transmission, pp.156-161-2001.

[5] X.G. Wu, A.Arulampalam, C. Zhan, and N.jenkins, "Application of a static reactive power compensator (STATCOM) and a dynamic braking resistor (DBR) for the stability enhancement of a large wind farms", Wind Engineering Journal, vol. 27, no.2, pp.93-106, March2003.