An Improved SVPWM based Shunt Active Power Filter for Compensation of Power System Harmonics

 ABSTRACT:

Space vector pulse width modulation (SVPWM) has been extensively utilized in the three-phase voltage source inverters (VSI) for the benefit of fixed switching frequency, full utilization of DC bus voltage and superior control. In recent times, SVPWM technique was applied for active power filter (APF) control application, as the APF is nothing but of a current controlled VSI. The conventional SVPWM based APF has high computational burden due to complex trigonometric

calculations and sector identification involved to generate the compensating signal, hence the response time for compensation is slow. In this paper, an improved SVPWM technique based shunt APF is presented based on the effective time concept. The effective time concept eliminates the trigonometric calculations and sector identification, thereby it reduces the computational effort. Simulation results demonstrate the efficacy of the APF with the improved SVPWM based control strategy. The response time for compensation is 0.02sec.

KEYWORDS:

1.      SVPWM

2.       Shunt APF

3.      VSI

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM

            

Figure 1. Configuration of Improved SVPWM based shunt APF

CIRCUIT DIAGRAM:

                       

             

Figure 2. Proposed SVPWM control for APF topology

EXPECTED SIMULATION RESULTS:

                      

            

Figure 3. Simulation results (a) Source voltages, (b) Load currents, (c) Compensated source currents, and (d) Filter currents (APF).

                          

                              

Figure 4.DC Bus voltage of the proposed shunt APF

CONCLUSION:

 In this paper, an improved SVPWM based shunt APF is proposed, which is suitable for digital control realization. This method requires less computation when compared to the conventional SVPWM technique as it eliminates the complex trigonometric calculation and sector identification, The performance of shunt APF with this proposed SVPWM method for harmonic compensation is examined and proved to be worthy where the THD of the source currents was reduced from 24.38% to 4.47% and the response time for harmonic compensation is 0.02 sec.

REFERENCES:

[1] H. Akagi, E. H. Watanabe, and M. Aredes, Instantaneous Power Theory and Applications to Power Conditioning, M. E. El-Hawari, Ed. New York: Wiley, 2007.

[2] Recommended Practice for Harmonic Control in Electric Power Systems, IEEE Std. 519-1992, 1992.

[3] Limits for Harmonic Current Emission, IEC 61000-3-2, 2001.

[4] H. Akagi, “New trends in active filters for power conditioning,” IEEE Trans. Ind. Appl., vol. 32, no. 2, pp. 1312–1332, Nov./Dec. 1996.

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

Integration Of Solar cells With Power Electronic Converters For Power Generation

 ABSTRACT:

An integration and operation of single phase bidirectional inverter with two buck/boost maximum power point trackers (MMPTs) is provided for dc distribution system. In a dc distribution system a bidirectional inverter is required to control the power flow between dc bus and ac grid, and to regulate the dc bus to the certain range of voltage. A droop regulation mechanism is followed to reduce the capacitor size and to balance the power flow between the dc bus and ac grid. The photovoltaic (PV) array voltage can be vary from 0 to 600V, especially with

thin-film PV panels, the MPPT topology is formed with buck and boost converters to operate at the dc-bus voltage around 380V, reducing the voltage stress of its followed inverter. In this paper

the fuzzy logic technique is used to control the bidirectional inverter for improve overall efficiency of the system and it is designed by using MATLAB/SIMULINK software.

KEYWORDS:

                    1.Bi-directional inverter

                    2. buck/boost MPPTs

                    3. dc distribution system

SOFTWARE: MATLAB/SIMULINK

SIMULINK DIAGRAM:

Figure 1. Overall Simu link Model

EXPECTED SIMULATION RESULTS:

Figure 2. Grid Voltage

Figure 3. dc-bus voltage

Figure 4 Buck/Boost Output Waveform

  

 Figure 5. Real and Reactive power

 CONCLUSION:

A single-phase bi-directional inverter with two buck/boost MPPTs has been designed by using the MATLAB/SIMULINK.A buck/boost inverter can be used for both the step-up and step-down process. The inverter controls the power flow between dc bus and ac grid, and regulates the dc bus to a certain range of voltages. Since the PV-array voltage can vary from 0 to 600 V, the MPPT topology is formed with buck / boost converters to operate at the dc-bus voltage around 380 V, reducing the voltage stress of its followed inverter. Also the controller can on-line check the input configuration of the MPPTs, equally distribute the PVarray output current to the two MPPTs in parallel operation, and switch control laws to smooth out mode transition. In this the fuzzy control technique has been used. Integration and operation of the overall inverter system have been discussed in detail, which contributes to ac grid as well as dc-distribution.

 REFERENCES:

[1] Shih-Ming Chen, Student Member, IEEE, Tsorng-Juu Liang, Senior Member, IEEE, Lung-Sheng Yang, and Jiann- Fuh Chen, Member, IEEE: “A Boost Converter With Capacitor Multiplier and Coupled Inductor for AC Module Applications” IEEE Transactions 2013.

[2] J.-M. Shen, H.-L. Jou, and J.-C. Wu, “Novel transformer less grid connected power converter with negativegrounding for photovoltaic generation system,” IEEE Transactions 2012.

[3] Tamás Kerekes, Member, IEEE, Remus Teodorescu, Senior Member, IEEE, Pedro Rodríguez, Member, IEEE,Gerardo Vázquez, Student Member, IEEE, and EmilianoAldabas, Member, IEEE: “A New High-Efficiency Single- Phase  Transformer less PV Inverter Topology” IEEE Transactions 2011.

[4] Loc Nguyen Khanh, Student Member, IEEE, Jae-Jin Seo, Yun-Seong Kim, and Dong-Jun Won, Member, IEEE: “Power-Management Strategies for a Grid-Connected PV-FC Hybrid System” IEEE Transactions 2010.

[5] T.-F. Wu,K.-H.Sun, C.-L.Kuo, and C.-H. Chang, “Predictive current controlled 5 kW single-phase bidirectional inverter with wide inductance variation for DC micro grid applications,” IEEE Transactions 2010.

Improved Direct Torque Control of Induction Motor

ABSTRACT:

Control of induction motor is most precisely required in many high performance applications. With the development in power electronic field various control methods for control of induction motor have been developed. Among these Direct torque control (DTC) seems to be particularly interesting, being independent of machine rotor parameters and requiring no speed or position sensors. In addition to the simple structure it also allows a good torque control in transient and steady state conditions. The disadvantage of using DTC is that it results in high torque and flux ripple and variable switching frequency of voltage source inverter, owing to the use of hysteresis controllers for torque and flux loop. In order to overcome these problems, various methods have been proposed by several researchers like variable hysteresis band comparators, space vector modulation, predictive control schemes and intelligent control techniques. However these methods have diminished the main feature of DTC that is simple control structure. This report presents constant switching frequency based torque and flux controllers to replace conventional hysteresis based controllers where almost fixed switching frequency with reduced torque and flux ripple is obtained by comparing the triangular waveforms with the compensated error signals

KEYWORDS:

                                 1.3-phase VSI

                                 2. torque controller

                                 3. flux controller

SOFTWARE:  MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Block diagram of conventional DTC method

Fig.2. MATLAB/SIMULINK Model of the DTC Drive

EXPECTED SIMULATION RESULTS:

            

Fig.3. Torque response (a) Conventional DTC scheme (b) Improved DTC Scheme

 Fig.4. Speed and Torque response for (a) Conventional DTC scheme (b) Improved DTC scheme

Fig.5. Circular flux locus (a) conventional DTC scheme (b) Improved DTC scheme

Fig.6. 3-phase line-line voltages and currents (a) Conventional DTC scheme (b) Improved DTC scheme

CONCLUSION:

In this paper a detailed comparison between the conventional DTC and improved DTC scheme is made with help of some Matlab simulation results and hence it is shown that a significant reduction in torque and flux ripple can be achieved with the improved DTC scheme also with improved controllers the switching frequency which is constant can be varied by varying the frequency of the triangular carrier waveforms of the torque controllers

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, Sep.–Oct. 1986.

[2] J-K. Kang, D-W Chung, S. K. Sul, (2001) “Analysis and prediction of inverter switching frequency in direct torque control of induction machine based on hysteresis bands and machine parameters”, IEEE Transactions on Industrial Electronics, Vol. 48, No. 3, pp. 545-553.

[3] D.Casadei, G.Gandi,G.Serra,A.Tani,(1994)“Switching strategies in direct torque control of induction machines,” in Proc. of ICEM’94, Paris (F), pp. 204-209.

[4] J-K. Kang, D-W Chung and S.K. Sul, (1999) “Direct torque control of induction machine with variable amplitude control of flux and torque hysteresis bands”, International Conference on Electric Machines and Drives IEMD’99,pp.640-642.

[5] Vanja Ambrozic, Giuseppe S. Buja, and Roberto Menis, ”Band- Constrained Technique for Direct Torque Control of Induction Motor”, IEEE Trans. On industrial electronics , vol. 51, no. 4, august 2004, pp.776-784

A New Hybrid Active Neutral Point Clamped Flying Capacitor Multilevel Inverter

 ABSTRACT:

This paper proposes a new five-level hybrid topology combining features of neutral point clamped and flying capacitor inverters. The proposed topology provides a tradeoff between different component counts to achieve a good loss distribution, avoid direct series connection of semiconductor devices, keep the balanced operation of dc-link capacitors while keeping the number of costly components such as capacitors and switches low. The required modulation strategy is developed and the operation of the proposed topology is studied. The features of the proposed topology are investigated and compared to other available topologies. Simulation results are provided to verify the performance of the converter for medium voltage applications

KEYWORDS:

              1 .Multilevel Inverter,

              2. Flying Capacitor,

              3. Active Neutral Point Clamped,

              4. Diode Clamped.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. A phase leg of the proposed 5-level hybrid topology.

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation results. (a) Phase voltage (b) Line voltage (c) Flying capacitor voltages (d) Load current

frequency 5kHz. The dc-link voltage is set at 18kV and flying capacitors are 330μF. It can be seen that even without an RLC balance booster, the capacitor voltage errors are limited to less than 4%.

CONCLUSION:

A new hybrid 5-level inverter topology and modulation technique is proposed. Compared to 5-level ANPC as the most similar topology, this new topology requires two less switches at the cost of an additional capacitor and six diodes. However, since the capacitors still see the switching frequency and their size remain the same, it is expected to reduce the inverter’s

total cost. Also, unlike 5-level ANPC, all switches must withstand the same voltage which eliminates the need for series connection of switches and associated simultaneous turn on

and off problem. Good loss distribution among switches can increase the inverters rated power    or provide higher switching frequency and smaller capacitor size.

REFERENCES:

[1] H. Abu-Rub, J. Holtz, and J. Rodriguez, “Medium-Voltage Multilevel Converters—State of the Art, Challenges, and Requirements in Industrial Applications,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2581–2596, Aug. 2010.

[2] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. G. Franquelo, J. Rodriguez, M. A. Pérez, and J. I. Leon, “Recent Advances and Industrial Applications of Multilevel Converters,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553–2580, Aug. 2010.

[3] M. Malinowski, K. Gopakumar, J. Rodriguez, and M. A. Pérez, “A Survey on Cascaded Multilevel Inverters,” IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 2197–2206, Jul. 2010.

[4] J. Rodriguez, “Multilevel inverters: a survey of topologies, controls, and applications,” IEEE Trans. Ind. Electron., vol. 49, no. 4, pp. 724–738, Aug. 2002.

[5] J. Rodriguez, S. Bernet, P. K. Steimer, and I. E. Lizama, “A Survey on Neutral-Point-Clamped Inverters,” IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 2219–2230, Jul. 2010.

Direct Torque Control of Induction Motor Drive With Flux Optimization

ABSTRACT:

MATLAB / SIMULINK implementation of the Direct Torque Control Scheme for induction motors is presented in this paper. Direct Torque Control (DTC) is an advanced control technique with fast and dynamic torque response. The scheme is intuitive and easy to understand as a modular approach is followed. A comparison between the computed and the reference values of the stator flux and electromagnetic torque is performed. The digital outputs of the comparators are fed to hysteresis type controllers. To limit the flux and torque within a predefined band, the hysteresis controllers generate the necessary control signals. The knowledge about the two hysteresis controller outputs along with the location of the stator flux space vector in a two dimensional complex plane determines the state of the Voltage Source Inverter (VSI). The output of the VSI is fed to the induction motor model. A flux optimization algorithm is added to the scheme to achieve maximum efficiency. The output torque and flux of the machine in the two schemes are presented and compared

KEYWORDS:

                          1.Direct Torque Control,

                          2. Induction Motor,

                          3. Flux Optimization

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1: Block Diagram of Conventional DTC Scheme

 

Figure 2: Block Diagram of the Flux Optimized DTC Scheme

EXPECTED SIMULATION RESULTS:

                              

Figure 3: Stator d-q flux space vector without flux optimization                     

                                   

 Figure 4: Stator d-q flux space vector with flux  optimization

                                  

Figure 5: Variation of Stator Flux – Conventional  DTC Scheme                                                                   

                                    

  Fig 6: Variation of Stator Flux - Optimized DTC scheme

                                                   

                                                            

      

Figure 7: Variation of Mechanical Speed – Conventional  optimized DTC scheme    

   

                                     

 Figure 8: Variation of Mechanical Speed - Optimized DTC scheme

                                         

Figure 9: Electromagnetic Torque - Conventional DTC

             

                                            

Figure 10: Electromagnetic Torque - Optimized  DTC

                                   

Figure 11: Percentage Efficiency of Flux Optimized DTC

CONCLUSION:

In this paper, DTC for an induction motor drive has been shown along with flux optimization algorithm. DTC is a high performance, robust control structure. A comparative analysis of the two DTC schemes, with and without flux optimization algorithm has been presented. With flux optimization implementation, it is observed that the efficiency of the about 87 % has been obtained. MATLAB simulation of a 15 Hp IM drive has been presented to confirm the results.

REFERENCES:

[1] Werner Leonhard. Control of Electric Drives. Springer-Verlag Berlin Heidelberg, 1996.

[2] F. Blaschke. “The Principle of Field Orientation as Applied to The New Transvector Closed Loop Control System for Rotating Field Machines”. Siemens Review, pages 217–220, 1972.

[3] K. Hasse. “On The Dynamic Behavior of Induction Machines Driven by Variable Frequency and Voltage Sources”. ETZ Archive, pages 77–81., 1968.

[4] I. Takahashi and T Nogushi. “A New Quick Reponse and High Efficiency Control Strategy of an Induction Motor”. IEEE Trans. Industry Applications, IA -22:820–827, 1986.

[5] M. Depenbrock. “Direct Self Control (DSC) of inverter-fed induction machines”. IEEE Trans. Power Electronics, 3(4):420–429, 1988