Enhancement of Voltage Quality in Isolated Power Systems

Enhancement of Voltage Quality in Isolated Power Systems

ABSTRACT

The use of series compensators (SCs) in improving voltage quality of isolated power systems is considered. The roles of the compensators are to mitigate the effects of momentary voltage sags/swells, and to control the level of harmonic distortions in the networks. A control strategy for the SC is developed to regulate power flow. This is achieved through phase adjustment of load terminal voltage. It leads to an increase in the ride through capability of loads to the voltage sags/swells. Validity of the technique is illustrated through simulation.

KEYWORDS

1.     Harmonic power flow

2.     Isolated power system

3.     phase shift

4.     Series compensation

SOFTWARE: Matlab/Simulink

BLOCK DIAGRAM:

Fig. 1.Typical isolated power system installed with an SC.

CONCLUSION:

Voltage quality improvement in an isolated power system through series compensation has been investigated. The power system contains significant proportion of fluctuating nonlinear load and a high level of harmonic distortions is observed. A method to control the injection voltage of the SC so that it can mitigate the effects of the harmonics has been proposed. The SC is also designed to maintain the fundamental frequency component of the terminal voltage of protected sensitive load. In the process of harmonic voltage compensation, it is shown that power exchange exists between the SC and the external network. Based on the analysis of the harmonic real power flow in the power system, it is seen that the SC would import harmonic real power from the external system. A new SC control strategy is then proposed which involves the phase adjustment of the fundamental frequency component of the sensitive load terminal voltage. Through the analysis on the power exchange it is shown that the load ride through capability during voltage sag can be improved with the support of the harmonic real power absorbed by the SC. The capacity of the SC required is modest and, therefore, makes it a viable device for such an application. Simulations have confirmed the effectiveness of the proposed method, as it is applied on the SC to achieve improved quality of supply in the power system.

REFERENCES:

[1] I. Jonasson and L. Soder, “Power quality on ships-a questionnaire evaluation concerning island power system,” in Proc. IEEE Power Eng. Soc. Summer Meeting, Jul. 2001, vol. 15–19, pp. 216–221.

[2] J. J. Graham, C. L. Halsall, and I. S. McKay, “Isolated power systems: Problems of waveform distortion due to thyristor converter loading,” in Proc. 4th Int. Conf. Power Electronics and Variable-Speed Drives, Jul. 1990, vol. 17–19, pp. 327–330.

[3] ITI (CBEMA) Curve Application Note, [Online]. Available: http://www.itic.org., Inf. Technol. Ind. Council (ITI).

[4] J. C. Das, “Passive filter—Potentialities and limitations,” IEEE Trans. Ind. Appl., vol. 40, no. 1, pp. 232–241, Jan. 2004.

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

A Novel Nine-Switch Inverter for Independent Control of Two Three-phase Loads

A Novel Nine-Switch Inverter for Independent Control of Two Three-phase Loads

ABSTRACT

Industrial applications require large numbers of motors. For example, motors are used to manipulate industrial robots, an electric vehicles with in-wheel motors and electric trains. Two methods exist for controlling PM motors providing an inverter to control each motor, and connecting the motors in parallel and driving them with a single inverter. The first method makes an experimental apparatus complex and expensive; the second does not allow independent control of each motor because of differences in rotor angle between the two motors. Thus, we propose a novel nine-switch inverter that can independently control two three-phase loads. This paper introduces the structure of the nine-switch inverter, which is made from nine switches. The

validity of the proposed inverter is verified through simulations and experiments.

BLOCK DIAGRAM:

Fig. 1. Block diagram of establishment of modulation rate.

CIRCUIT DIAGRAM:

Fig. 2.Main circuit of proposed nine-switch inverter

CONCLUSION:

This paper proposes a nine-switch inverter and a PWM method that can independently control two three-phase loads. The simulations and the experiments were performed to verify the validity of the proposed inverter. The results confirmed that the nine-switch inverter can independently control amplitude and frequency for two three-phase loads, and permanent magnet synchronous motors; however, there is some ripple amplitude, and slight interference between Inv1 and Inv2. Work is needed to improve of the interference problem.

REFERENCES:

[1] Yusuke Nozawa, Motoki Hizume, Yuta Kimura, Kazuo Oka, and Kouki Matsuse, “Independent Position Control of Two Permanent Magnet Synchronous Motors with Five–Leg Inverter By the Expanded Two–Arm Modulation Method”, IEEJ Industry Applications Society Conference, 2005, (in Japanese)

[2] Tsutomu Kominami and Yasutaka Fujimoto, “Magnetic Levitation Control and Spiral-Linear Transformation System for Spiral Motor”, IEEE Int. Workshop on Advanced Motion Control, vol. 2, pp. 529-534, 2006

[3] Tsutomu Kominami and Yasutaka Fujimoto, “Proposal of a Nine-Switch Inverter That Can Independently Control Two PM Motors”, IEEJ Industry Applications Society Conference, pp. 187-190, 2006, (in Japanese)

[4] Kazuo Oka and Kouki Matsuse, “A Nine-Switch Inverter for Driving Two AC Motors Independently”, IEEJ Trans. on Electrical and Electronic Engineering, 2007

[5] Tsutomu Kominami and Yasutaka Fujimoto, “Development of a Nine- Switch Inverter That Can Independently Control Two Loads”, IEEJ Annual Meeting Record, pp. 133-134, 2007, (in Japanese)

Simulink Model of Direct Torque Control of Induction Machine

Simulink Model of Direct Torque Control of Induction Machine

ABSTRACT

 Direct torque control (DTC) is one of the most excellent control strategies of torque control in induction machine. It is considered as an alternative to the field oriented control (FOC) or vector

control technique. These two control strategies are different on the operation principle but their

objectives are the same. They aim to control effectively the torque and flux. Torque control of an

induction machine based on DTC strategy has been developed and a comprehensive study is present in this research. The performance of this control method has been demonstrated by simulations performed using a versatile simulation package, Matlab/Simulink. Several numerical simulations have been carried out in a steady state and transient operation on a speed control mode.

KEYWORDS

1. Direct torque control

2. Induction machine

3. Vector control

4. Matlab/Simulink

SOFTWARE: Matlab/Simulink

BLOCK DIAGRAM:

                        Fig.1 Direct torque control of induction machine

                  Fig. 2: Developed model of direct torque control of induction machine

     

CONCLUSION:

The work carried out in this paper is aimed and focused to develop a direct torque control simulink model. The DTC architecture allows the independent and decoupled control of torque and stator flux. The implementation of the DTC model has been deeply described and justified its realization. In order to show the effectiveness of the model, a numerical simulation has been performed on a 7.5 kW induction machine fed by an IGBT PWM inverter. The feasibility and the

validity of the developed DTC model, based on switching table technique, have been proved by simulation results obtained in the torque control mode.

REFERENCES:

1.     Casadei, D., G. Gandi, G. Serra and A. Tani, 1994. Effect of flux and torque hysteresis band amplitude in direct torque control of Induction Machine. Proc. IECON’94, Bologna, Italy, 299-304.

2.      Casadei, D., F. Profumo, G. Serra and A. Tani, 2002. FOC and DTC: two viable schemes for induction motors torque control. IEEE Trans. Power Electronics, 17(5): 779-787.

3.     3. Chapuis, Y.A. and D. Roye, 1998. Direct torque control and current limitation method in start up of an induction machine. IEE Conf. Power Electronics and Variable Speed Drives, 451-455

4.     4. Takahashi, I. and Y. Ohmori, 1989. High Performace direct torque control of induction motor. IEEE Trans. Ind. Appl. 25 (2): 257-264.

5.      Vas, P., 1990. Vector Control of a.c. machines.Oxford University Press.

Study on Speed Sensor less SVM-DTC System of PMSM

ABSTRACT:

A novel speed sensorless direct torque control system-SVM-DTC of permanent magnet synchronous motor(PMSM) based on SVM and MRAS is presented. In this paper the various components of the speed sensorless SVM-DTC and the principle of realization are discussed in detail. Finally the simulation results with the application of MATLAB/Simulink show that the speed identification algorithm is accurate and of robustness, moreover, the whole control system has good static and dynamic performances.

KEYWORDS:

1.      Permanent magnet synchronous motor (PMSM)

2.      Space Vector Modulation (SVM)

3.      Direct torque control (DTC)

4.      Model reference adaptive system (MRAS)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

CONCLUSION:

In this paper, the speed sensorless SVM-DTC system based on SVM and MRAS is presented and the control system has a clear control principle and structure. Simulation results show that the speed identification algorithm can estimate accurately the real speed and has robustness to varying of stator resistor. Moreover the speed sensorless SVM-DTC system has good static and dynamic performance.

 REFERENCES:

[1] Yen-Shin Lai, Jian-Ho Chen, A New Approach to Direct Torque Control of Induction Motor Drives for Constant Inverter Switching Frequency and Torque Ripple Reduction[J], IEEE Transactions on Energy Conversion,2001,16(3): 220-227

[2] Liang yan, Li Yongdong. The state of art of sensor-less vector control of PMSM[J]. Electric Drive,2003,33(4):4-9

[3] Young Sam Kim, Sang Kyoon Kim,Young Ahn Kwon,MRAS Based Sensorless Control of Permanent Magnet Synchronous Motor[C] . SICE Annual Conference, Fukui, Japan, 2003:1632-1637

[4] Li Yongdong. AC motor digital control system [M]. Beijing: Machine Press,2002

[5] Li Su. Direct Torque Control of Induction Motor[M]. Beijing: Machine Press,1999

Modeling and Simulating For Transient Stability Analysis of Power System Using Dynamic Phasor

ABSTRACT:

In this paper, using a new solution method, the phasor simulation, a model of two-machine power system with static var compensators (SVC) and power system stabilizers (PSS) is built. By this system model, the transient stability analysis of this two machine power system when single-phase fault and 3-phase fault is simulated. The result shows that the phasor solution method can reduce simulation time greatly of power grids ,and has good precision.

KEYWORDS:

1.      Multi-machine power system

2.      Static var compensators (SVC)

3.       Transient stability

4.      Simulation

5.      Dynamic phasor

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

CONCLUSION:

Through apply the phasor solution method to modeling and simulation for the transient stability analysis of a simple transmission system containing two hydraulic power plants, shows that the phasor solution method can reduce the system simulation time greatly and has good precision. This solution method still can be applied to simulate more complex power grids.

REFERENCES:

[1] Venkatasubramanian V．Tools for dynamic analysis of the general large power system using time-varying phasors[J]. International Journal on Electric Power and Energy Systems，1994，16(6),pp365-376．

[2] Henschel S，Ibrahim A I，Dommel H W．Transmission line model for variable step size simulation algorithms[J]．Electrical Power and Energy Systems，1999，21(3),pp191-198．

[3] Stankovic A M,Mattavelli P, Caliskan V, et al. Modeling and analysis of FACTS devices with dynamic phasors. IEEE Power Engineering Society Winter Meeting,2000, 2,pp1440-1446.

[4] Mattavelli P，Verghese G C，Stankovic A M．Phasor dynamics of thyristor-controlled series capacitor systems[J] ． IEEE Trans on Power Systems，1997，12(3),pp1259-1267．

[5]Aleksandar M，Stankovic¡ä，Timur Aydin．Analysis of asymmetrical faults in power systems using dynamic phasors[J]．IEEE Trans．on Power Systems，2000，15(3),pp1062-1068．

A Non-Insulated Step-Up/Down DC-DC Converter With Wide Range Conversion

ABSTRACT:

 In this paper an approach of a step-up/down dc-dc converter with wide range conversion called Boost²-Buck is presented. The proposed converter presents nonpulsating input and output current. It has operations equivalent to a cascade converter consisting of two boost converter and one buck converter, but with the advantage of using single active switch. Mathematical analysis and experimental results are presented for converter operating with output power of 20W.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

CONCLUSION:

The boost²-buck converter presented in this paper provides a wide range of dc conversion when compared with the conventional non-insulated dc-dc converters. This topology presents non pulsating input and output current. It has operations equivalent to a cascade converter consisting of two boost converter and one buck converter, but with the advantage of using single active switch. Consequently, when compared with a converter cascade, it is cheaper, less bulky and uses circuit control simpler. Through the experimental results is possible to prove the performance of the converter as well as the theoretical analysis presented.

REFERENCES:

[1] J. A. Morales-Saldaña, J. Leyva-Ramos, E. E. Carbajal-Gutiérrez, M. G. Ortiz-Lopez, “Average Current-Mode Control Scheme for a Quadratic Buck Converter with a Single Switch,” IEEE Trans. on Power Electronics, vol. 23, pp. 485–490, Jan. 2008.

[2] J. R. de Britto, A. E. Demian Jr., E. A. A. Coelho, L. C. de Freitas, V. J. Farias, J. B. Vieira Jr., “A Proposal of Led Lamp Driver for Universal Input Using Cuk Converter,” IEEE 39th Power Electronics Specialists Conference, Rhoedes, 2008.

[3] J. R. de Britto, A. E. Demian Jr., E. A. A. Coelho, L. C. de Freitas, V. J. Farias, J. B. Vieira Jr., “LED Lamp Driver Using a Converter with Wide Range Conversion Microcontroller-Based,” 34th Annual Conference of the IEEE Industrial Electronics Society (Accepted), Orlando, 2008.

[4] J. A. Morales-Saldaña, J. Leyva-Ramos, E. E. Carbajal-Gutiérrez, “Modeling of Switch-Mode DC-DC Cascade Converters,” IEEE Trans. on Aerospace and Electronic Systems, vol. 38, pp. 295–299, Jan. 2002. 

A Variable-Speed, Sensorless, Induction Motor Drive Using DC Link Measurements

A Variable-Speed, Sensorless, Induction Motor Drive

Using DC Link Measurements

ABSTRACT:

This paper presents a new control strategy for three-phase induction motor which includes independent speed & torque control loops and the current regulation thereby overcoming the limitation (i.e. sluggish response) of volts per hertz controlled industrial drives. For close-loop control, the feedback signals including the rotor speed, flux and torque are not measured directly but are estimated by means of an algorithm. The inputs to this algorithm are the reconstructed waveforms of stator currents and voltages obtained from the dc link and not measured directly on stator side. The proposed drive thus requires only one sensor in the dc link to implement the close-loop speed and torque control of a three-phase induction motor. The simulation results on a 2.2 kW induction motor drive in Matlab/Simulink software show fast dynamic response and good agreement between the actual values and the estimated values of torque and speed. Replacement of the open-loop control strategy of existing v/f drive by the proposed close-loop strategy appears to be possible without requiring any additional power components and sensors.

KEYWORDS:

1. Speed-sensorless

2. Estimation

3. Dc link

4. Band-pass filter

5. Reconstruction

6.Three-phase induction motor

7.Space-vector.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

                                              Figure 1. Block diagram of the proposed scheme.

CONCLUSION:

In this paper, a new control strategy for induction motor drive is proposed. The drive is operated under torque control with an outer speed loop and is very similar to open-loop v/f drive in terms of power components and sensors required. Due to the inclusion of torque control loop, the drive response is fast and stable. Simulation results confirm the effectiveness of the proposed scheme. The technique uses only dc link voltage and dc link current measurements to generate the estimates of the dc link voltage is assumed as constant, only one current sensor in the dc link is sufficient to give the estimates of all required feedback variables. Moreover, the same current sensor that is already available in the dc link of an open-loop v/f drive for protection purpose can be used. Thus the open loop control strategy in an existing v/f drive can be replaced by the proposed close-loop control strategy without requiring any additional power components or the physical sensors. The proposed strategy appears to be a good compromise between the high-cost, high-performance field-oriented drives and the low-cost, low-performance v/f drives. Practical implementation of the proposed scheme on a 16 bits floating point arithmetic Texas Instrument TMS320C31 processor are the subject of future follow-up research work.

REFERENCES:

[1] B. K. Bose, Power Electronics and Motor Drives, Delhi, India, Pearson Education, Inc., 2003.

[2] M. Rodic and K. Jezernik, “Speed-sensorless sliding-mode torque control of induction motor,” IEEE Trans. Ind. Electron., vol. 49, no. 1, pp. 87-95, Feb. 2002.

[3] L. Harnefors, M. Jansson, R. Ottersten, and K. Pietilainen, “Unified sensorless vector control of synchronous and induction motors,” IEEE Trans. Ind. Electron., vol. 50, no. 1, pp. 153-160, Feb. 2003.