Novel Direct Torque Control Based On Space Vector Modulation With Adaptive Stator Flux Observer For Induction Motors

ABSTRACT:

This paper describes a combination of direct torque control (DTC) and space vector modulation (SVM) for an adjustable speed sensorless induction motor (IM) drive. The motor drive is supplied by a two-level SVPWM inverter. The inverter reference voltage is obtained based on input-output feedback linearization control, using the IM model in the stator – axes reference frame with stator current and flux vectors components as state variables. Moreover, a robust full-order adaptive stator flux observer is designed for a speed sensorless DTC-SVM system and a new speed-adaptive law is given. By designing the observer gain matrix based on state feedback 􀀀 control theory, the stability and robustness of the observer systems is ensured. Finally, the effectiveness and validity of the proposed control approach is verified by simulation results.

KEYWORDS:

1.      Adaptive stator flux observer

2.      Direct torque control

3.       Feedback linearization

4.      Robust

5.      Space vector modulation

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1.The block diagram of the DTC-SVM system

CONCLUSION:

A novel DTC-SVM scheme has been developed for the IM drive system, which is on the basis of input-output linearization control. In this control method, a SVPWM inverter is used to feed the motor, the stator voltage vector is obtained to fully compensate the stator flux and torque errors. Furthermore, a robust full-order adaptive flux observer is designed for a speed sensorless DTC-SVM system. The stator flux and speed are estimated synchronously. By designing the constant observer gain matrix based on state feedback H∞  control theory, the robustness and stability of the observer systems is ensured. Therefore, the proposed sensorless drive system is capable of steadily working in very low speed, has much smaller torque ripple and exhibits good dynamic and steady-state performance.

REFERENCES:

[1] I. Takahashi and T. Noguchi, “A new quick-response and high efficiency control strategy of an induction motor,” IEEE Trans. Ind. Appl., vol. IA-22, no. 5, pp. 820–827, 1986.

[2] Y. S. Lai and J. H. Chen, “A new approach to direct torque control of induction motor drives for constant inverter switching frequency and torque ripple reduction,” IEEE Trans. Energy Convers., vol. 16, no. 3, pp. 220–227, 2001.

[3] S. Mir, M. E. Elbuluk, and D. S. Zinger, “PI and fuzzy estimators for tuning the stator resistance in direct torque control of induction machines,” IEEE Trans. Power Electron., vol. 13, no. 2, pp. 279–287, 1998.

[4] F. Bacha, R. Dhifaoui, and H. Buyse, “Real-time implementation of direct torque control of an induction machine by fuzzy logic controller,” in Proc. ICEMS, 2001, vol. 2, pp. 1244–1249.

[5] A. Arias, J. L. Romeral, and E. Aldabas, “Fuzzy logic direct torque control,” in Proc. IEEE ISIE, 2000, vol. 1, pp. 253–258.

Simulation of a Shunt Active Power Filter using MATLAB /SIMULINK

ABSTRACT:

Along with increasing demand on improving power quality, the most popular technique that has been used is Active Power Filter (APF); this is because APF can easily eliminate unwanted harmonics, improve power factor and overcome voltage sags. This paper will discuss and analyze the simulation result for a three-phase shunt active power filter using MATLAB/SIMULINK program. This simulation will implement a non-linear load and compensate line current harmonics under balance and unbalance load. As a result of the simulation, it is found that an active power filter is the better way to reduce the total harmonic distortion (THD) which is required by quality standards IEEE-519.

KEYWORDS:

1.      APF

2.       d-q theorem,

3.      THD

4.       Power Quality

5.      ADS

6.       Instantaneous Power theory

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Diagram illustrating component of shunt connected active filter with the waveform showing cancellation of harmonics from an ASD load

CONCLUSION:

The Increasing usage of non-linear load in electrical power system which will produce the current and voltage harmonics and associate harmonics problem in power system become more serious and directly affecting the power quality. Conventional way of harmonics elimination by using passive filter might suffer from parasitic problem. It has been shown that three phase active filter based on p-q theory can be implemented for harmonic mitigation and power factor correction. Harmonics mitigation carried out by the active filter meets the IEEE-519 standard requirements.

REFERENCES:

[1] A. Emadi, A. Nasiri, and S. B. Bekiarov, “Uninterruptible Power Supplies and Active Filter”, Florida, 2005, pp. 65-111.

[2] D. W. Hart, “Introduction to Power Electronics”, New Jersey, 1997, pp. 291-335.

[3] M. McGranaghan, “Active Filter Design and Specification for Control of Harmonics in Industrial and Commercial Facilities”, 2001.

[4] S. Round, H. Laird and R. Duke, “An Improved Three-Level Shunt Active Filter”, 2000.

[5] H. Lev-Ari, “Hilbert Space Techniques for Modeling and Compensation of Reactive Power in Energy Processing Systems”, 2003.

A FACTS Device Distributed Power Flow Controller (DPFC)

A FACTS Device  Distributed Power Flow

Controller (DPFC)

ABSTRACT:

This paper presents a new component within the flexible ac-transmission system (FACTS) family, called distributed power-flow controller (DPFC). The DPFC is derived from the unified

power-flow controller (UPFC). The DPFC can be considered as a UPFC with an 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 employs the distributed FACTS (D-FACTS) concept, which is to use multiple small-size single-phase converters instead of the one 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. Accordingly, 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. The principle and analysis of the DPFC are presented in this paper and the corresponding experimental results that are carried out on a scaled prototype are also shown.

KEYWORDS:

1.     AC–DC power conversion

2.     Load flow control

3.     Power electronics

4.     Power semiconductor devices

5.     Power-transmission control.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. DPFC control block diagram.

CONCLUSION:

This paper has presented a new concept called DPFC. The DPFC emerges from the UPFC and inherits the control capability of the UPFC, which is the simultaneous adjustment of the line impedance, the transmission angle, and the bus-voltage magnitude. The common dc link between the shunt and series converters, which is used for exchanging active power in the UPFC, is eliminated. This power is now transmitted through the transmission line at the third-harmonic frequency. The series converter of the DPFC employs the D-FACTS concept, which uses multiple small single-phase converters instead of one large-size converter. 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. The DPFC concept has been verified by an experimental setup. 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.

REFERENCES:

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

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

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

[4] A.-A. Edris, “Proposed terms and definitions for flexible ac transmission system (facts),” IEEE Trans. Power Del., vol. 12, no. 4, pp. 1848–1853, Oct. 1997.

[5] 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.

Seven Level Shunt Active Power Filter for High Power Drive Systems

Seven Level Shunt Active Power Filter for

High Power Drive Systems

ABSTRACT:

In high-power adjustable-speed motor drives, such as those used in electric ship propulsion systems, active filters provide a viable solution to mitigating harmonic related issues caused by diode or thyristor rectifier front-ends. To handle the large compensation currents and provide better thermal management, two or more paralleled semiconductor switching devices can be used. In this paper, a novel topology is proposed where two active filter inverters are connected with tapped reactors to share the compensation currents. The proposed active filter topology can also produce seven voltage levels, which significantly reduces the switching current ripple and the size of passive components. Based on the joint redundant state selection strategy, a current balancing algorithm is proposed to keep the reactor magnetizing current to a minimum. It is shown through simulation that the proposed active filter can achieve high overall system performance. The system is also implemented on a real-time digital simulator to further verify its effectiveness.

KEYWORDS:

1.     Active filters

2.     Harmonic analysis

3.     Power conversion

4.     Power electronics.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Active filter connection to a shipboard power system.

CIRCUIT DIAGRAM:

Fig. 2. Proposed seven-level active filter topology.

                                                                                                                   

CONCLUSION:

A new type of power converter has been introduced in this paper. The converter is based on parallel connection of phase legs through an interphase reactor. However, the reactor has an off center tap at one-third resulting in an increased number of voltage levels. Specifically, two three-level flying capacitor phase legs are paralleled in this way to form a seven-level power converter. The converter is utilized in an active filter application. The details of the high-level control as well as the switching control have been presented. The control ensures reactor current sharing as well as flying capacitor voltage balance. The proposed active filter has been validated for a naval ship board power system using detailed simulation and RTDS hardware.

REFERENCES:

[1] 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, Oct. 1999.

[2] S. Bhattacharya, T.M. Frank, D. M. Divan, and B. Banerjee, “Active filter system implementation,” IEEE Ind. Appl. Mag., vol. 4, no. 5, pp. 47–63, Sep. 1998.

[3] Z. Du, L. M. Tolbert, and J. N. Chiasson, “Active harmonic elimination for multilevel converters,” IEEE Trans. Power Electron., vol. 21, no. 2, pp. 459–469, Mar. 2006.

[4] M. E. Ortuzar, R. E. Carmi, J. W. Dixon, and L. Moran, “Voltage-source active power filter based on multilevel converter and ultracapacitor DC link,” IEEE Trans. Ind. Electron., vol. 53, no. 2, pp. 477–485, Apr. 2006.

[5] B. R. Lin and T. Y. Yang, “Analysis and implementation of a three-level active filter with a reduced number of power semiconductors,” Proc. Inst. Electr. Eng. Electr. Power Appl., vol. 152, no. 5, pp. 1055–1064, Sep. 2005.

Modeling and Simulation of a Distribution STATCOM (D-STATCOM) for Power Quality Problems Voltage Sag and Swell Based on Sinusoidal Pulse Width Modulation (SPWM)

Modeling and Simulation of a Distribution

STATCOM (D-STATCOM) for Power Quality

Problems Voltage Sag and Swell Based on

Sinusoidal Pulse Width Modulation (SPWM)

ABSTRACT:

This paper presents the systematic procedure of the modeling and simulation of a Distribution STATCOM (DSTATCOM) for power quality problems, voltage sag and swell based on Sinusoidal Pulse Width Modulation (SPWM) technique. Power quality is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure of end use equipments. The major problems dealt here is the voltage sag and swell. To solve this problem, custom power devices are used. One of those devices is the Distribution STATCOM (D STATCOM), which is the most efficient and effective modern custom power device used in power distribution networks. D-STATCOM injects a current in to the system to correct the voltage sag and swell. The control of the Voltage Source Converter (VSC) is done with the help of SPWM. The proposed D-STATCOM is modeled and simulated using MATLAB/SIMULINK software.

KEYWORDS:

1.     Distribution STATCOM (D-STATCOM)

2.     MATLAB/SIMULINK

3.     Power quality problems

4.     Sinusoidal Pulse Width Modulation (SPWM)

5.     Voltage sag and swell

6.     Voltage Source Converter (VSC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Schematic representation of the D-STATCOM for a typical custom power application

Fig. 2. Control scheme and test system implemented in MATLAB/SIMULINK to carry out the D-ST ATCOM simulations

CONCLUSION:

This paper has presented the power quality problems such as voltage sags and swell. Compensation techniques of custom power electronic device D-ST ATCOM was presented. The design and applications of D-STATCOM for voltage sags, swells and comprehensive results were presented. The Voltage Source Convert (VSC) was implemented with the help of Sinusoidal Pulse Width Modulation (SPWM). The control scheme was tested under a wide range of operating conditions, and it was observed to be very robust in every case. For modeling and simulation of a D-ST ATCOM by using the highly developed graphic facilities available in MATLAB/SIMULINK were used. The simulations carried out here showed that the D-STA TCOM provides relatively better voltage regulation capabilities.

REFERENCES:

 [I] O.Anaya-Lara, E. Acha, "Modeling and analysis of custom power systems by PSCAD/EMTDC," IEEE Trans. Power Delivery, vol. 17, no . I, pp. 266-272, January 2002.

[2] S. Ravi Kumar, S. Sivanagaraju, "Simualgion of D-Statcom and DVR in power system," ARPN jornal of engineering and applied science, vol. 2, no. 3, pp. 7-13, June 2007.

[3] H. Hingorani, "Introducing custom power", IEEE Spectrum, vol. 32, no. 6, pp. 41-48, June 1995.

[4] N. Hingorani, "FACTS-Flexible ac transmission systems," in Proc. IEE 5th Int Conf AC DC Transmission, London, U.K., 1991, Conf Pub. 345, pp. 1-7.

[5] Mahesh Singh, Vaibhav Tiwari, "Modeling analysis and soltion to power quality problems," unpublished.

Fault Ride-Through of a DFIG Wind Turbine Using a Dynamic Voltage Restorer During Symmetrical and Asymmetrical Grid Faults

ABSTRACT:

The application of a dynamic voltage restorer (DVR) connected to a wind-turbine-driven doubly fed induction generator (DFIG) is investigated. The setup allows the wind turbine system an uninterruptible fault ride-through of voltage dips. The DVR can compensate the faulty line voltage, while the DFIG wind turbine can continue its nominal operation as demanded in actual grid codes. Simulation results for a 2 MW wind turbine and measurement results on a 22 kW laboratory setup are presented, especially for asymmetrical grid faults. They show the effectiveness of the DVR in comparison to the low-voltage ride-through of the DFIG using a crowbar that does not allow continuous reactive power production.

KEYWORDS:

1.      Doubly fed induction generator (DFIG)

2.       Dynamic voltage restorer (DVR)

3.       Fault ride-through and wind energy

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

CONCLUSION:

The application of a DVR connected to a wind-turbine-driven DFIG to allow uninterruptible fault ride-through of grid voltage faults is investigated. The DVR can compensate the faulty line

voltage, while the DFIG wind turbine can continue its nominal operation and fulfill any grid code requirement without the need for additional protection methods. The DVR can be used to protect already installed wind turbines that do not provide sufficient fault ride-through behavior or to protect any distributed load in a microgrid. Simulation results for a 2 MW wind turbine under an asymmetrical two-phase grid fault show the effectiveness of the proposed technique in comparison to the low-voltage ridethrough of the DFIG using a crowbar where continuous reactive power production is problematic. Measurement results under transient grid voltage dips on a 22 kW laboratory setup are presented to verify the results.

REFERENCES:

[1] M. Tsili and S. Papathanassiou, “A review of grid code technical requirements for wind farms,” Renewable Power Generat., IET, vol. 3, no. 3, pp. 308–332, Sep. 2009.

[2] R. Pena, J. Clare, and G. Asher, “Doubly fed induction generator using back-to-back pwm converters and its application to variable-speed windenergy generation,” Electr. Power Appl., IEE Proc., vol. 143, no. 3, pp. 231–241, May 1996.

[3] S.Muller,M.Deicke, andR.DeDoncker, “Doubly fed induction generator systems for wind turbines,” IEEE Ind. Appl.Mag., vol. 8, no. 3, pp. 26–33, May/Jun. 2002.

[4] J. Lopez, E. Gubia, P. Sanchis, X. Roboam, and L. Marroyo, “Wind turbines based on doubly fed induction generator under asymmetricalvoltage dips,” IEEE Trans. Energy Convers., vol. 23, no. 1, pp. 321–330, Mar. 2008.

A Single-Phase Z-Source Buck–Boost Matrix Converter

ABSTRACT:

This paper proposes a new type of converter called a single-phase Z-source buck–boost matrix converter. The converter can buck and boost with step-changed frequency, and both the frequency and the voltage can be stepped up or stepped down. In addition, the converter employs a safe-commutation strategy to conduct along a continuous current path, which results in the elimination of voltage spikes on switches without the need for a snubber circuit. The operating principles of the proposed single-phase Z-source buck–boost matrix converter are described, and a circuit analysis is provided. To verify the performance of the proposed converter, a laboratory prototype was constructed with a voltage of 40 Vrms /60 Hz and a passive RL load. The simulation and the experimental results verified that the converter can produce an output voltage with three different frequencies 120, 60, and 30 Hz, and that the amplitude of the output voltage can be bucked and boosted.

KEYWORDS:

1.      Buck–boost voltage

2.       single-phase matrix converter

3.      step-up and step-down frequency

4.       Z-source converter

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

          Fig.1. General block diagram of the proposed topology

CONCLUSION:

In this paper, we have proposed a new single-phase Z-source buck–boost matrix converter that can buck and boost to the desired output voltage with step-changed frequency. The output of this single-phase Z-source buck–boost matrix converter produces the voltage in buck–boost mode with a step-changed frequency, in which the output frequency is either an integer multiple or an integer fraction of the input frequency. It also provides a continuous current path by using a commutation strategy. The use of this safe-commutation strategy is a significant improvement as it makes it possible to avoid voltage spikes on the switches without the use of a snubber circuit. We presented a steady-state circuit analysis and described the operational stages. To verify the performance of the proposed converter, we constructed a laboratory prototype with an input voltage of 40 Vrms (57 Vpeak)/60 Hz based on TMS320F2812 DSP, and we performed a PSIM simulation.

The simulation and the experimental results with a passive RL load showed that the output voltage can be produced at three different frequencies, 120, 60, and 30 Hz, and in the buck–boost amplitude mode. Because of limitations in the power laboratory setup, the prototype was intended only to verify the operational concept. We expect that this proposed strategy can be used in various industrial applications that require step-changed frequencies and variable voltage amplitudes. The proposed converter is particularly suitable for controlling the speed of a fan or a pump without the use of an inverter because for these applications, the input voltage frequency must be changed to control their speed by stages.

REFERENCES:

 [1] P. C. Loh, R. Rong, F. Blaabjerg, and P.Wang, “Digital carrier modulation and sampling issues of matrix converters,” IEEE Trans. Power Electron., vol. 24, no. 7, pp. 1690–1700, Jul. 2009.

[2] Y. D. Yoon and S. K. Sul, “Carrier-based modulation technique for matrix converter,” IEEE Trans. Power Electron., vol. 21, no. 6, pp. 1691–1703, Nov. 2006.

[3] M. Jussila and H. Tuusa, “Comparison of simple control strategies of space-vector modulated indirect matrix converter under distorted supply voltage,” IEEE Trans. Power Electron., vol. 22, no. 1, pp. 139–148, Jan. 2007.

[4] I. Sato, J. Itoh, H. Ohguchi, A. Odaka, and H. Mine, “An improvement method of matrix converter drives under input voltage disturbances,” IEEE Trans. Power Electron., vol. 22, no. 1, pp. 132–138, Jan. 2007.

[5] C. Liu, B. Wu, N. R. Zargari, D. Xu, and J. Wang, “A novel threephase three-leg ac/ac converter using nine IGBTs,” IEEE Trans. Power Electron., vol. 24, no. 5, pp. 1151–1160, May 2009.