Analysis of Discrete & Space Vector PWM Controlled Hybrid Active Filters For Power Quality Enhancement

 ABSTRACT:

It is known from the fact that Harmonic Distortion is one of the main power quality problems frequently encountered by the utilities. The harmonic problems in the power supply are caused by the non-linear characteristic based loads. The presence of harmonics leads to transformer heating, electromagnetic interference and solid state device mal-functioning. Hence keeping in view of the above concern, research has been carried out to mitigate harmonics. This paper presents an analysis and control methods for hybrid active power filter using Discrete Pulse Width Modulation and Space Vector Pulse Width Modulation (SVPWM) for Power Conditioning in distribution systems. The Discrete PWM has the function of voltage stability, and harmonic suppression. The reference current can be calculated by‘d-q’ transformation. In SVPWM technique, the Active Power Filter (APF) reference voltage vector is generated instead of the reference current, and the desired APF output voltage is generated by SVPWM. The THD will be decreased significantly by SVPWM technique than the Discrete PWM technique based Hybrid filters. Simulations are carried out for the two approaches by using MATLAB, it is observed that the %THD has been improved from 1.79 to 1.61 by the SVPWM technique.

KEYWORDS:

1.      Discrete PWM Technique

2.      Hybrid Active Power Filter

3.      Reference Voltage Vector

4.      Space Vector Pulse Width Modulation (SVPWM)

5.       Total Harmonic Distortion (THD)

6.      Voltage Source Inverter (VSI)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1. Configuration of an APF using SVPWM

EXPECTED SIMULATION RESULTS:

             

Figure 2. Source current waveform with hybrid filter

Figure 3. FFT analysis of source current with hybrid filter

Figure 4. Simulation results of balanced linear load

(a) The phase-A supply voltage and load current waveforms

(b) The phase-A supply voltage and supply current waveforms

Figure 5. Simulation results of unbalanced linear load

(a) Three-phase load current waveforms

(b) Three-phase supply current waveforms

Figure 6. Simulation results of non-linear load

(a) The three-phase source voltage waveforms

(b) The three-phase load current waveforms

(c) The three-phase source current waveforms

Figure 7. Harmonic spectrum of non-linear load

(a) The phase-A load current harmonic spectrum

(b) The phase-A source current harmonic spectrum

CONCLUSION:

In this paper, a control methodology for the APF using Discrete PWM and SVPWM is proposed.

These methods require a few sensors, simple in algorithm and are able to compensate harmonics and unbalanced loads. The performance of APF with these methods is done in MATLAB/Simulink. The algorithm will be able to reduce the complexity of the control circuitry. The harmonic spectrum under non-linear load conditions shows that reduction of harmonics is better. Under unbalanced linear load, the magnitude of three-phase source currents are made equal and also with balanced linear load the voltage and current are made in phase with each other. The simulation study of two level inverter is carried out using SVPWM because of its better utilization of DC bus voltage more efficiently and generates less harmonic distortion in three-phase voltage source inverter. This SVPWM control methodology can be used with series APF to compensate power quality distortions. From the simulated results of the filtering techniques, it is observed that Total Harmonic Distortion is reduced to an extent by the SVPWM Hybrid filter when compared to the Discrete PWM filtering technique i.e. from 1.78% to 1.61%.

REFERENCES:

[1] EI-Habrouk. M, Darwish. M. K, Mehta. P, “Active Power Filters-A Rreview,” Proc.IEE-Elec. Power Applicat., Vol. 147, no. 5, Sept. 2000, pp. 403-413.

[2] Akagi, H., “New Trends in Active Filters for Power Conditioning,” IEEE Trans. on Industry applications,Vol. 32, No. 6, Nov-Dec, 1996, pp. 1312-1322.

[3] Singh.B, Al-Haddad.K, Chandra.A, “Review of Active Filters for Power Quality Improvement,” IEEE Trans. Ind. Electron., Vol. 46, No. 5, Oct, 1999, pp. 960-971.

[4] Ozdemir.E, Murat Kale, Sule Ozdemir, “Active Power Filters for Power Compensation Under Non-Ideal Mains Voltages,” IEEE Trans. on Industry applications, Vol.12, 20-24 Aug, 2003, pp.112-118.

Space Vector Pulse Width Modulation Fed Direct Torque Control Of Induction Motor Drive Using Matlab-Simulink

 ABSTRACT:

Now a day’s induction motor drives are highly demanding to design both mechanical and electrical drive system which is used widely in many industrial applications. Recent years many mathematical models for induction motor drive using Simulink models are employed. Scalar and Vector control method can be applied to induction motors in three phases symmetric as well as unsymmetrical two-phase form. The mathematical and Simulink operation of the induction motor drive can be studied and it is equivalent to a DC motor by the vector control method. With the combined performance of the numerical electronics and power electronics we are capable to smoothly control the variable speed and torque in low power industrial operations. With the help of technological achievements, several command and control techniques are developed by the technologists to control the time, flux and torque of the industrial electrical machine drives. The direct torque control (DTC) technique is one of the most advanced mechanisms in control operation of torque and speed. This technique with SVPWM gives fine regulation without rotational speed controlled feedback. The electromagnetic torque and stator flux are estimated in DTC technique only stator currents and voltage and it is independent of the parameters of the motor except for the Rs i.e. stator resistance [7].

KEYWORDS:

1.      Controller

2.      DTC

3.      IDM

4.      SVPWM and switching table.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. DTC block diagram

 EXPECTED SIMULATION RESULTS:

Fig.2. Electromagnetic torque

Fig.3. Rotor speed

Fig.4. Stator current

Fig.5. d-axis stator flux

Fig.6. q-axis stator flux

Fig.7. Electromagnetic torque

Fig.8. Rotor speed

Fig.9. Trajectory of direct axis stator and quadrature axis

flux (stationary reference frame)

Fig.10. Electromagnetic torque

Fig.11. Rotor speed

Fig.12. Direct axis stator flux

Fig.13. Quadrature axis stator flux

Fig.14. Direct axis stator current

Fig.15. Quadrature axis stator current

Fig.16. Stator flux trajectory

Fig.17. Rotor flux trajectory

CONCLUSION:

The proposed paper highlights to create a Simulink model of  DTC in induction motor drive. The DTC technique allows the decoupled control of torque and stator flux operate indipendently. The control process is simulated with the help of simpower system MATLAB Simulink block set and Sector determination with open-loop induction motor drive is obtained. In conventional DTC technique, high torque ripple is produced because the voltage space vector which are considered is applied for the whole switching period without considering the torque error value. This torque ripple can be minimized in order to achieve a smooth operation of the drive system and its performances, by changing the duty cycle ratio of the voltage vector which are selected during each switching cycle period, based on the stator flux position and torque error magnitude. This constitutes the basic of SVPWM technique. here simulate DTC scheme based on SVPWM technique and comparative study of conventional DTC-SVM scheme is derived and studied.

REFERENCES:

[1] Takahashi Isao, Noguchi Toshihiko, ,,’’A New Quick-Response IEEE Transactions on Industry Applications , Vol. IA-22No-5, Sept/Oct 1986.

Direct Torque Control of Brushless DC Drives With Reduced Torque Ripple

 ABSTRACT:

The application of direct torque control (DTC) to brushless ac drives has been investigated extensively. This paper describes its application to brushless dc drives, and highlights the essential differences in its implementation, as regards torque estimation and the representation of the inverter voltage space vectors. Simulated and experimental results are presented, and it is shown that, compared with conventional current control, DTC results in reduced torque ripple and a faster dynamic response.

KEYWORDS:

1.      Brushless dc (BLDC) drives

2.      Direct torque control (DTC)

3.      Permanent-magnet motor

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Schematic of DTC BLDC drive.

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulated results for Motor 1 (1500 r/min). (a) Phase-to-ground voltage. (b) Phase voltage. (c) Phase current. (d) Locus of stator flux linkage. (e) Electromagnetic torque.

Fig. 3. Simulated results for Motor 2 (400 r/min). (a) Phase-to-ground voltage. (b) Phase voltage. (c) Phase current. (d) Locus of stator flux linkage. (e) Electromagnetic torque.

CONCLUSION:

DTC has been applied to a BLDC drive, and its utility has been validated by simulations and measurements on two BLDC motors which have very different back-EMF waveforms. The main difference between the implementation of DTC to BLAC and BLDC drives is in the estimation of torque and the representation of the inverter voltage vectors. It has been shown that DTC is capable of instantaneous torque control and, thereby, of reducing torque pulsations.

REFERENCES:

[1] J. R. Hendershort Jr and T. J. E. Miller, Design of Brushless Permanent- Magnet Motors. Oxford, U.K.: Magana Physics/Clarendon, 1994.

[2] T. Kenjo and S. Nagamori, Permanent-Magnet and Brushless DC Motors. Oxford, U.K.: Clarendon, 1985.

[3] P. J. Sung,W. P. Han, L. H. Man, and F. Harashima, “A new approach for minimum-torque-ripple maximum-efficiency control of BLDC motor,” IEEE Trans. Ind. Electron., vol. 47, no. 1, pp. 109–114, Feb. 2000.

[4] C. French and P. Acarnley, “Direct torque control of permanent magnet drives,” IEEE Trans. Ind. Appl., vol. 32, no. 5, pp. 1080–1088, Sep./Oct. 1996.

[5] T. S. Low, K. J. Tseng, K. S. Lock, and K.W. Lim, “Instantaneous torque control,” in Proc. Fourth Int. Conf. Electrical Machines and Drives, Sep. 13–15, 1989, pp. 100–105.

b

A Novel Direct Torque Control Scheme for Induction Machines With Space Vector Modulation

ABSTRACT:

In this paper a new method for Direct Torque Control (DTC) based on load angle control is developed. The use of simple equations to obtain the control algorithm makes it easy tu understand and implement. Fixed switching frequency and low torque ripple are obtained using space vector modulation. This control strategy overcomes the must important drawbacks of classic DTC. Results shows the feasibility of the proposed method, obtaining good speed control bandwidth while overcoming classic DTC drawbacks.

KEYWORDS:

1.      Electric Drives

2.      AC Machines

3.      Direct Torque Control

4.      Space Vector Modulation

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 Fig.  1. Classic DTC control block diagram

EXPECTED SIMULATION RESULTS:

Fig. 2. Comparison of dynamic response klween DTC-SVM.F ield Oriented Control and Classic DTC. (a) Field Oriented Control. (b) Classic Direct Torque Control. (e) proposed Method.

Fig. 3. Torque response comparison between DTC-SVM and classic DTC. (a) Field Onenled Control, (h) Classic Direct Torque Control, (c) Proposed Method.

Fig. 4. Size of hysteresis band and sampling frequency effects on torque

ripple for clasic DTC.

Fig. 5. Torque spectral analJsis cornpanson. (a) DTC-SVM torque spectrum,

(b) Classic DTC torque spectrum.

Fig. 6. Stator Current during speed reversal.

.CONCLUSION:

The DTC-SVM strategy proposed in this work to control flux and torque is based on few induction machine fundamental equations. Consequently, the control method is simple and easy to implement. No coordinate rotation and less PI controllers than in field oriented control are needed. 0.1 (1.2 0.3 0.4 0.5 0.6 In addition, the proposed DTC strategy is well suited for use lime Is] in conjunction with space vector modulation resulting in a powerful alternative to overcome the well known drawbacks Fig. IO. Stator Current during speed reversal. of the original DTC solution: variable switching frequency and high torque ripple.

REFERENCES:

[1] F. Blaschke. “A New Method for the Estructural Decoupling of AC Induction Machines”. Cmj Rec. IFAC, Duessektorf. Genmny, pages 1-15, Oct. 1971.

[2] 1. Takahashi, Y. Ohmori. “High-Performance Direct Torque Control of an Induction Motor?. IEEE Trons. on Indu.~rriol Applicutions, 25(2):257- 262. MarcWApril 1989.

[3] M. Depenbmk. “Direct Self-Control (DSC) of Inverter-Fed Induction Machine”. IEEE Trans. on Power Elecrronicr. 3(4):42M29, October 1988.

[4] D. Casadei. G. Sera, A. Tani. “Implementation of a Direct Torque Control Algorithm for Induction Motors Based on Discrete Space Vector Modulation”. IEEE Trans. on Power Electronics. 15(4):769-777, July 2Mm.

[5] C. Manins, X. Roboarn. T.A. Meynard. A. Carvalho. “Switching frequency lmposition and Ripple Reduction in DTC Drives by Using a Multilevel Converer”. IEEE Trans. on Power Electmnicr. 17(2):28& 297, March 2002.