Natural Harmonic Elimination of Square-Wave Inverter for Medium-Voltage Application

ABSTRACT:

In this paper, a low-frequency square-wave inverter with a series-connected pulse width modulation (PWM) inverter is investigated for high-power applications. The series compensators produce only the desired harmonic voltages to make the net output voltage sinusoidal with small PWM switching harmonics only. An open-loop control strategy for the series compensator is proposed in this paper. This strategy indirectly sets the compensator dc bus voltage to the desired level. No external dc source or active power at fundamental frequency is required to control this dc bus voltage. Different variations of this basic strategy are presented in this paper for medium voltage applications. Theoretical analysis of this strategy is presented in this paper with simulation and experimental results.

KEYWORDS:

1.      AC motor drives

2.      Power conversion

3.      Power conversion harmonics.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 EXPECTED SIMULATION RESULTS:

CONCLUSION:

In this paper, an open-loop natural control of voltage source inverter has been proposed mainly for high-power applications. The main square-wave inverter is built with high-voltage low switching- frequency semiconductor devices like integrated gate commutated thyristors (IGCTs). The series compensators are IGBT-based inverters and operate from relatively low dc bus voltages at high switching frequencies. The series compensators produce only the desired harmonic voltages to make the net output voltage sinusoidal. For medium-voltage application, several compensating PWM inverters are connected in series. Each cell compensates one particular harmonic only. As the order of harmonics increases, the required dc bus voltage level drops. This enables to exploit higher switching frequency for higher order harmonic cell. It has been established both theoretically and experimentally that the dc bus of the compensators do not require any external dc source or closed-loop controller for this proposed strategy. The active power at harmonic frequencies keeps the compensator dc bus voltage charged. For variable speed drives applications, the magnitude of the fundamental output voltage should be controlled by regulating the dc bus voltage of the square-wave inverter. For static synchronous compensator (STATCOM) applications, the limited variation of this dc bus voltage may also be required. This can be achieved by drawing small active power at fundamental frequency from the grid.

REFERENCES:

 [1] A. Nabae, I. Takahashi, and H. Akagi, “A new neutral point clamped PWM inverter,” IEEE Trans. Ind. Appl., vol. IA-17, no. 5, pp. 518–523, Sept./Oct. 1981.

[2] M. D.Manjrekar, P. K. Steimer, and T. A. Lipo, “Hybrid multilevel power conversion system: A competitive solution for high-power applications,” IEEE Trans. Ind. Appl., vol. 36, no. 3, pp. 834–841, May/Jun. 2000.

[3] R. H. Wilkinson, T. A. Meynard, and H. du T. Mouton, “Natural balance of multicell converters: The general case,” IEEE Trans. Power Electron., vol. 21, no. 6, pp. 1649–1657, Nov. 2006.

[4] H. Akagi, S. Inoue, and T. Yoshii, “Control and performance of a transformer less cascade PWM STATCOM with star configuration,” IEEE Trans. Ind. Appl., vol. 43, no. 4, pp. 1041 1049, Jul./Aug. 2007.

[5] S. S. Fazel, S. Bernet, D. Krug, and K. Jalili, “Design and comparison of 4-kV neutral-point-clamped, flying-capacitor, and series-connected Hbridge multilevel converters,” IEEE Trans. Ind. Appl., vol. 43, no. 4, pp. 1032–1040, Jul./Aug. 2007.

Improved Z-Source Inverter with Reduced Z-Source Capacitor Voltage Stress and Soft-Start Capability

ABSTRACT:

This paper proposes an improved Z-source inverter topology. Compared to the traditional Z source inverter, it can reduce the Z-source capacitor voltage stress significantly to perform the same voltage boost, and has inherent limitation to inrush current at startup. The control strategy of the proposed Z-source inverter is exactly the same as the traditional one, so all the existing control strategy can be used directly. A soft-start strategy is also proposed to suppress the inrush surge and the resonance of Z-source capacitors and inductors. The operation principle of the proposed topology and comparison with the traditional topology are analyzed in detail. Simulation and experimental results are given to demonstrate the new features of the improved topology.

KEYWORDS:

1.      Inrush current

2.      Soft start

3.      Z-source inverter.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 EXPECTED SIMULATION RESULTS:

CONCLUSION:

This paper has presented a new Z-source inverter topology. Compared to the previous Z-source inverter, the improved topology has several merits.

1) The Z-source capacitor voltage stress is reduced greatly to perform the same boost ability; thus, low-voltage capacitors can be utilized to reduce the system cost and volume;

2) The inrush current and resonance of Z-source capacitors and inductors in traditional topology can be suppressed with a proper soft-start strategy. Simulation and experimental results verified the aforesaid merits of the proposed topology.

REFERENCES:

 [1] F. Z. Peng, “Z-source inverter,” IEEE Trans. Ind. Appl., vol. 39, no. 2, pp. 504–510, Mar./Apr. 2003.

[2] Q. Tran, T. Chun, J. Ahn, and H. Lee, “Algorithms for controlling both the DC boost and AC output voltage of Z-source inverter,” IEEE Trans. Ind. Electron., vol. 54, no. 5, pp. 2745–2750, Oct. 2007.

[3] F. Z. Peng, M. Shen, and Z. Qian, “Maximum boost control of the Z-source inverter,” IEEE Trans. Power Electron., vol. 20, no. 4, pp. 833–838, Jul. 2005.

[4] M. Shen, J. Wang, A. Joseph, F. Z. Peng, L. M. Tolbert, and D. J. Adams, “ConstantBoost control of the Z-source inverter to minimize current ripple and voltage stress,” IEEE Trans. Ind. Appl., vol. 42, no. 3, pp. 770–777, May/Jun. 2006.

[5] P. C. Loh, D. M. Vilathgamuwa, Y. S. Lai, G. T. Chua, and Y. Li, “Pulsewidth modulation of Z-source inverters,” IEEE Trans. Power Electron., vol. 20, no. 6, pp. 1346–1355, Nov. 2005.

COMPENSATION OF SAGS AND SWELLS VOLTAGE USING DYNAMIC VOLTAGE RESTORER (DVR) DURING SINGLE LINE TO GROUND AND THREE-PHASE FAULTS

ABSTRACT:

This paper deals with modelling and simulation technique of a Dynamic Voltage Restore (DVR). The DVR is a dynamic solution to protect sensitive loads against voltage sags and swells. The DVR can be implemented to protect a group of medium voltage or low voltage consumers. The new configuration of DVR has been proposed using improved d-q-0 controller technique. This study presents compensation of sags and swells voltage during single line to ground (SLG) fault and three-phase fault. Simulation results carried out by Matlab/Simulink verify the performance of the proposed method.

KEYWORDS:

1.      Dynamic Voltage Restorer

2.      Voltage Sags

3.      Voltage Swells

4.      Single Line to Ground (SLG) Fault

5.      Three-Phase Fault.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

CONCLUSION:

The DVR modeling and simulation has been shown by the aid of Matlab/Simulink. The control system is based on dq0 technique which is a scaled error, between source side of the DVR and its reference for compensating sags and swells. The simulation shows that the DVR performance is efficient in mitigation of voltage sags and swells. According to the simulation results, the DVR is able to compensate the sags and swells during single line to ground (SLG) fault and three-phase fault. As result of the FFT analysis, the compensated load voltage by the DVR has appropriate THD. The DVR handles both balanced and unbalanced situations without any difficulties. It injects an appropriate voltage component to correct any anomaly rapidly in the supply voltage; in addition, it keeps the load voltage balanced and constant at the nominal value.

REFERENCES:

[1] D.M. Vilathgamuwa, A.A.D.R. Perera, S.S. Choi, “Voltage Sag Compensation with Energy Optimized Dynamic Voltage Restorer”, IEEE Trans. on Power Del., Vol. 11, No. 3, pp. 928-936, July 2003.

[2] P. Boonchiam, N. Mithulananthan, “Understanding of Dynamic Voltage Restorers through Matlab Simulation”, Thammasat Int. J. Sc. Tech., Vol. 11, No. 3, July-Sept. 2006.

[3] IEEE Std. 1159-2009, “Recommended Practice for Monitoring Electric Power Quality”, pp. 1-81 June 2009.

[4] V. Salehi, S. Kahrobaee, S. Afsharnia, “Power Flow Control and Power Quality Improvement of Wind Turbine Using Universal Custom Power Conditioner”, IEEE Conference on Industrial Electronics, Vol. 4, pp. 1688-1892, July 2002.

[5] B.H. Li, S.S. Choi, D.M. Vilathgamuwa, “Design Considerations on the Line-Side Filter Used in the Dynamic Voltage Restorer”, IEE Proc. Gener. Transmission Distrib., Issue 1, Vol. 148, pp. 1-7, Jan. 2001.

Comparison of Control Algorithms for Shunt Active Filter for Harmonic Mitigation

ABSTRACT:

 Shunt Active Filter generates the reference current, that must be provided by the power filter to compensate harmonic currents demanded by the load. This paper presents different types of SRF methods for real time regeneration of compensating current for harmonic mitigation. The three techniques analyzed are the Synchronous Reference Frame Theory (SRF), SRF theory without synchronizing circuit like phase lock loop (PLL) also called instantaneous current component theory and finally modified SRF theory. The performance of Shunt Active Power Filter in terms of THD (Total Harmonic distortion) of voltage and current is achieved with in the IEEE 519 Standard. The comparison of all methods is based on the theoretical analysis and simulation results obtained with MATLAB/SIMULINK

KEYWORDS:

1.      Synchronous Reference Frame

2.      Instantaneous current component theory

3.      Modified SRF

4.      Active Filter

5.      Harmonics

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

CONCLUSION:

This paper presents the compensation performance of all the different SRF techniques under sinusoidal voltage source condition as shown in table-1. Results are similar with gained source THD under IEEE 519, but under various filter type the chebyshev type filter is having superior performance compare to Butterworth filter for all methods. The Synchronous Reference Frame method is one of the most common and performing methods for detection of harmonics in active filters. An Improved Synchronous Reference Frame Method for the control of active power filters was presented. It is called Filtered Modified Reference Frame Method (FMRF) and is based on the same principle as the Synchronous Reference Frame method. However, this new method explores the fact that the performance of the active filter to isolate harmonics depends on the speed of the system that determines the rotating reference frame, but doesn’t depend on its position. So, the delay introduced by the ac voltage filters, used for the detection of the reference frame, has no influence on the detection capability of the method. Compared with other methods, this new method presents some advantages due to its simplicity and its rudeness to perturbations on the ac network.

REFERENCES:

[1] M.J. Newman, D.N.Zmood, D.G.Holmes, “Stationary frame harmonic reference generation for active filter systems”, IEEE Trans. on Ind. App., Vol. 38, No. 6, pp. 1591 – 1599, 2002.

[2] V.Soares,P.Verdelho,G.D.Marques,“ An instantaneous active reactive current component method for active filters” IEEE Trans. Power Electronics, vol. 15, no. 4, July- 2000, pp. 660–669.

[3] G.D.Marques, V.Fernao Pires, Mariusz Mlinowski, and Marian Kazmierkowski, “An improved synchronous Reference Method for active filters,” the International conference on computer as a tool, EUROCON 2007, Warsaw, September - 2007, pp. 2564-2569. 

Comparison of Controllers for Power Quality Improvement Employing Shunt Active Filter

ABSTRACT:

In this paper, an implementation of shunt active filter for current harmonics compensation in order to achieve power quality improvement under non linear load condition is proposed. Shunt active filter makes the source current almost sinusoidal under non linear load condition by eliminating current harmonics. Controller generates the reference current and it is compared with actual current. PWM current controller controls the switch of the shunt active filter circuit. Shunt active filter eliminates the undesired current harmonics by injecting current into the system thereby reduces total harmonic distortion and improves power factor. The main objective of the project is to find the most suitable control method that is capable of reducing total harmonic distortion in the source current under non linear load condition. Fast and precise control loop is needed in order to assure the desired power quality. Three control techniques have been proposed: PI controller, Hysteresis current controller, Fuzzy logic controller. The system is modeled using Matlab/Simulink and simulation results prove that the source current harmonics can be reduced and power factor can be improved. The comparative performance of the proposed three controllers is also presented.

KEYWORDS:

1.      Power Quality

2.      Shunt Active Filter

3.      Voltage Source Inverter

4.      PI

5.      Hysteresis Current Controller

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

EXPECTED SIMULATION RESULTS:

CONCLUSION:

In this paper, the design of shunt active filter to compensate harmonics in the power system based on three control techniques were presented and compared. All the control techniques make the source voltage and source current to be in phase. In the first control scheme the capacitor voltage is regulated based on reference voltage and provides compensation for the reduction of harmonics in the source current, the second one provides compensation based on reference current generated from the fourier transform of load current, while the third one considers the active filter controlled by fuzzy logic controller which is suitable for uncertainty condition. Among the three proposals the fuzzy logic control technique [7] doesn't need any mathematical model, reduces total harmonic distortion in a better way and provides good performance and robust to the parameter uncertainties compared with other strategies.

REFERENCES:

[1] David A .Torrey, Adel M. A . M. AI-Zamel "Single-phase active power filters for multiple nonlinear loads" IEEE Transactions on Power Electronics, Vol. 1 0, No. 3, May 1 995, pp 263-2 72.

[2] B.Singh ,K.Ai-Haddad, and A.chandra , " A review of active filters for power quality improvement" IEEE Transaction on Industrial electronics, vol 46,Issue no. 5, Oct-1999, pp 960-971.

[3] Fabiana Pottker de Souza, and Ivo Barbi, " Single-phase active power filters for distributed power factor correction", Power Electronics Specialists Conference 2000, PESC 00, Vol.l , pp500-505.

[4] M. EI- Habrouk, M.K. Darwish and P. Mehta "Active filter - A review" Electric Power Applications, lEE Proceedings, Vol 1 4 7, Sep 2000, Issue 5, pp 403-413.

Control Strategy for Three Phase Voltage Source PWM Rectifier based on the SVM

Control Strategy for Three Phase Voltage Source PWM Rectifier based on the SVM

ABSTRACT:

This paper proposes the space vector pulse width modulation control scheme for three phase voltage source PWM rectifier. The control system based on SVPWM includes two PI controllers which are used to regulate the AC currents and DC link voltage. The proposed control can stabilize the minimum of the systems storage function at the desired equilibrium point determined by unity power factor and sinusoidal current on the AC side, and constant output voltage on the DC side. So the stable state performance and robustness against the load’s disturbance of PWM rectifiers are both improved. The result simulation shows feasibility of this strategy.

KEYWORDS:

1.      PWM rectifier

2.      SVPWM

3.      Power factor.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT SCHEMATIC DIAGRAM:

EXPECTED SIMULATION RESULTS:

CONCLUSION:

In this paper, a control strategy of the three phase voltage source PWM rectifier based on the space vector modulation is proposed. The control system based on SVPWM includes two PI controllers which are used to regulate the AC current and an outer DC voltage loop is composed by IP controller with anti-windup strategy. The simulation results shows a good performance of proposed strategy method at start-up and during load variations, providing a good regulation of output DC voltage, sinusoidal input AC current and unitary power factor.

REFERENCES:

[1] S. Mazumder, DSP based implementation of a PWM AC/DC/AC converter using space vector modulation with primary emphasis on the analysis of the practical problems involved, in 12th Applied Power Electronics Conference, 1997, pp. 306-312.

[2] S. Hansen, M. Malinowski, F. Blaabjerg, M.P. Kazmierkowski, Control strategies for PWM rectifier without line voltage sensors, in Proc. IEEE-APEC conf. vol. 2, pp. 832-839, 2000.

[3] Li Yabin, Li Heming, P. Yonglong, A unity power factor three phase buck type SVPWM rectifier based on direct phase control scheme, Mobile Robots,

Power Electronics and Motion Control Conference, 2006, IPEMC’06, vol. 8, no. 2, pp. 520-531.

[4] C.T. Pan and J. Shieh, New space vector control strategies for three-phase step-up/down AC/DC converter, IEEE Trans. On Industriel Electronics, vol. 47, pp. 25-35, February 2000.

[5] S.R. Bowes, S. Grewal, Novel harmonic elimination PWM control strategies for three-phase PWM inverters using space vector techniques, Electric Power Applications, IEE proceeding, vol. 146, pp. 451-495, Sept. 1999.

Z-SOURCE INVERTER WITH A NEW SPACE VECTOR PWM ALGORITHM FOR HIGH VOLTAGE GAIN

Z-SOURCE INVERTER WITH A NEW SPACE VECTOR PWM ALGORITHM FOR HIGH VOLTAGE GAIN

ABSTRACT:

 This paper presents a methodology to apply a novel space vector pulse width modulation control for three phase Z-source inverter. The space vector modulation for the conventional voltage source inverter is modified so that the additional shoot-through states are inserted within the zero states. So zero voltage time period is diminished for generating a shoot-through time, and active states are unchanged. The shoot-through states are evenly distributed to each phase within zero state. The shoot-through time is used for controlling the dc link voltage boost and hence the output voltage boost of the inverter. This new method provides a high voltage gain at higher modulation index. The proposed algorithm is verified with simulation and experiment. MatLab/Simulink is used for simulating the complete circuit with RL load. The frequency spectra of the output voltage and current are explored.

KEYWORDS:

1.      voltage gain

2.      Z-source inverter

3.      Space vector PWM

4.      Current source inverter

5.       Total harmonic distortion.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

EXPECTED SIMULATION RESULTS:

CONCLUSION:

A novel modified space vector PWM control method was carried out in this paper for three phase Z-source inverter. In this modified SVPWM method four shoot-through states were inserted in each sector for controlling the output voltage of Z-source inverter. The output AC voltage obtained from ZSI is no longer limited and can be boosted beyond the limit imposed by conventional VSI. Using MatLab/Simulink software package the simulation was performed to validate the proposed algorithm. The frequency spectra and the total harmonic distortion of the load current and voltages were obtained. Also the presented concepts were verified experimentally using a laboratory prototype.

REFERENCES:

[1] F. Z. Peng. 2003. Z-Source Inverter. IEEE Transactions on Industry Applications. 39(2): 504-510.

[2] P. C. Loh, D. M. Vilathgamuwa, Y. S. Lai, G. T. Chua and Y. W. Li. 2005. Pulse-width modulation of Z-source inverters. IEEE Trans. Power Electronics. 20: 1346-1355.

[3] Mohan N., W. P. Robbin and T. Undeland. 1995. Power Electronics: Converters, Applications and Design. 2^nd Edition, Wiley.

[4] F. Z. Peng, M. Shen and Z. Qian. 2005. Maximum Boost Control of the Z-source Inverter. IEEE Trans. Power Electronics. July. 20(4): 833-838.

[5] Miaosen shen, Jin Wang, Alan Joseph, Fang Z. Peng, Leon m. Tolbert and Donald J. Adams. 2006. Constant Boost Control of the Z-Source Inverter to Minimize Current Ripple and Voltage Stress. IEEE Transactions on Industry Applications. 42(3): 770-778.