A seventeen-level inverter with a single DC link for motor drives

           

ABSTRACT:  

In the present paper, a novel topology for generating a 17–level inverter using three-level flying capacitor inverter and cascaded H-bridge modules with floating capacitors. The proposed circuit is analyzed and various aspects of it are presented in the paper. This circuit is experimentally verified and the results are shown. The stability of the capacitor balancing algorithm has been verified during sudden acceleration. This circuit has many pole voltage redundancies. This circuit has an advantage of balancing all the capacitor voltages instantaneously by switching through the redundancies. Another advantage of this topology is its ability to generate all the 17 pole voltages from a single DC link which enables back to back converter operation. Also, the proposed inverter can be operated at all load power factors and modulation indices. Another advantage is, if one of the H-bridges fail, the inverter can still be operated at full load with reduced number of levels.

KEYWORDS:

1.      Seventeen level inverter

2.       Multilevel inverter

3.      Flying Capacitor

4.       Cascaded H-bridge

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

       

Fig.1. Proposed seventeen level inverter configuration formed by cascading three level flying capacitor inverter with 3 H-bridges using a Single DC link.

EXPECTED SIMULATION RESULTS:

         

                                                                  (a)

                                                                    (b) 

                        

                                                                    (c)

                  

                                                                    (d)

Fig.2: Voltages of  Capacitors C2, C3, C4 along with the phase current IA

(a)  10Hz operation, VAC4: (100V/div), VAC3: (10V/div), VAC2: (25V/div),IA:5A/div, Timescale: (20 mS/div).

(b)  20Hz operation, VAC4: (20V/div), VAC3: (10V/div), VAC2: (25V/div),IA:2A/div, Timescale: 10mS/div

(c)  30Hz operation, VAC4: (20V/div), VAC3: (10V/div), VAC2: (25V/div),IA:2A/div, Timescale: 10mS/div

(d)  40Hz operation, VAC4: (10V/div), VAC3: (10V/div), VAC2: (100V/div), IA:2A/div,Timescale:5mS/div

                          

                                 

                           

                                                                       (a)

                       

                                                                       (b)

                          

                                                                       (c)

                            

                                                                      (d)

Fig.3: Voltages of  Cap1 with Pole voltage VAO, Phase A Voltage VAN and  phase current IA. 

(a)   10Hz operation, VAC1( 50V/div), VAO: Pole voltage( 100V/div),VAN: Phase Voltage (100V/div),  IA: 2A/div, Timescale: (20mS/div).

(b)  20Hz operation, VAC1: ( 50V/div), VAO: Pole voltage( 100V/div),VAN: Phase Voltage (100V/div),  IA: 2A/div, Timescale: (10mS/div).

(c)    30Hz operation, VAC1: ( 50V/div), VAO: Pole voltage( 100V/div), VAN: Phase Voltage (100V/div),  IA: 2A/div, Timescale: (10mS/div).

(d)    40Hz operation, VAC1: ( 50V/div), VAO: Pole voltage( 100V/div),VAN: Phase Voltage (100V/div),  IA: 2A/div, Timescale: (10mS/div).

                    

                                                                      (a)

                                                                        (b)

Fig.4.  Performance of the capacitor balancing algorithm during sudden acceleration at no load from 10Hz to 40Hz  (a) VAC1:Cap AC1 voltage(100V/div), VAO: Pole Voltage(100V/div) , VAN: Phase Voltage(100V/div), IA: Phase current(2A/div)  (b) VAC4:Cap AC4 voltage(10V/div), VAC3:Cap AC3 voltage (20V/div), VAC2:Cap AC2 voltage (20V/div), IA: Phase current(2A/div)

CONCLUSION:

A  seventeen  level  inverter  formed  by  cascading  a  three level  flying  capacitor  with  floating  capacitor  H-bridges  has been proposed. The proposed inverter has reduced number of  switches as compared with standard configurations.  The  inverter  has  other  advantages  like  ability  to  balance  all  the  capacitor voltages at all  load currents and power  factors  there  by  generating  seventeen  pole  voltages  with  very  little  distortion.   Another advantage of  the  inverter  is ability  to generate all  the  required  voltage  levels  using  a  single  DC  link.  This  possibility  of  using  single  DC  link  enables  back  to  back  converter  operation  where  a  front  end  can  be  used  so  that  power  can  be  drawn  and  supplied  to  grid  at  desired  power  1%#' factor. Another important advantage is if one of devices in one of H-bridges fail, the inverter can still be operated at full load at reduced number of levels.  The proposed  inverter  is  analyzed  and  its  performance  is  experimentally  verified  for  various  modulation  indices  and  load  currents  by  running  a  three  phase  3kW  squirrel  cage  induction  motor.  The  stability  of  the  capacitor  balancing  algorithm  has  been  tested  experimentally  by  suddenly  accelerating  the motor  at no  load  and observing  the  capacitor  voltages at various load currents.

REFERENCES:

 [1] L. G. Franquelo, J. Rodriguez, J. I. Leon, S. Kouro, R. Portillo, M.A.M.  Prats,  “The  age  of multilevel  converters  arrives,”  IEEE  Ind.  Electron.  Magazine, vol. 2, no. 2, pp. 28–39, June.2008.

[2] S.  Kouro,  M.  Malinowski,  K.  Gopakumar,  J.  Pou,  L.  G.  Franquelo,  B.Wu, J. Rodriguez, M. A. Perez, 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] 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,  Sep. 1981. 

[4] M. Marchesoni, M. Mazzucchelli, and S. Tenconi, “A non-conventional  power  converter  for  plasma  stabilization,”  in  Proc.  IEEE  19th  Annu.  Power  Electron.  Spec. Conf.  (PESC’88) Rec., Apr.  11–14,  vol.  1,  pp.  122–129.

[5] Z.  Du,  L.M.  Tolbert,  J.  N.  Chiasson,  B.  Ozpineci,  H.  Li,  and  A.  Q.  Huang,  “Hybrid  cascaded H-bridges multilevel motor drive  control  for  electric vehicles,” in Proc. IEEE 37th Power Electron. Spec. Conf., Jun.  18–22, 2006, pp. 1–6.

Modeling and Simulation of Micro-grid Based on Small-hydro

ABSTRACT:

As a renewable resource, small hydro is gaining more and more attention due to its variable advantages. The paper focuses on the operation of the micro-grid based on small-hydro. A simulation model of the micro-grid is established by Simulink, which takes the following two cases into account, the grid-connected operation and isolated operation. Under these two cases, the differences of the excitation voltage and rotator speed are analyzed respectively. Power quality of the voltage is also analyzed. Faults are pre-set in the grid and micro-grid. Then the operations of the micro-grid when faults happen are simulated. By comparison of the results, the effects of the fault-cutting-off time are discussed.

KEYWORDS:

1.      Small-hydro

2.       Micro-grid

3.       Model

4.       Simulation

5.      Faults

SOFTWARE: MATLAB/SIMULINK

 SIMULING BLOCK DIAGRAM:

 Fig. 1. Simulation model of the entire system

EXPECTED SIMULATION RESULTS:

             

  Fig. 2. Field voltage of generator

             

                                            

    Fig. 3. Rotator speed of generator

 

                                

    Fig. 4. Output voltage (RMS) of generator 1(THD=0.80%)

                              

                               

      Fig. 5. Active power assumption of load 1

                                    

                                

         Fig. 6. Field voltage of generator

    

                               

 Fig. 7. Rotator speed of generator

                              

 

  Fig. 8. Output voltage (RMS) of generator 1(THD=1.91%) 

 

  

   Fig. 9. Active power assumption of load 1

        

       Fig. 10. Field voltage of generator

         

 Fig. 11. Rotator speed of generator

              

    Fig. 12. Output voltage (RMS) of generator 1

 

         

Fig. 13. Active power assumption of load 1

 

                                    

  Fig. 14. Field voltage of generator     

         Fig. 15. Rotator speed of generator

 

    

       Fig. 16. Output voltage (RMS) of generator 1

 

       

Fig. 17. Active power assumption of load 1

          

   Fig. 18. Field voltage of generator

                                    

                                  

Fig. 19. Rotator speed of generator

 

                                 

  Fig. 20. Output voltage (RMS) of generator 1

                                  

 

Fig. 21. Active power assumption of load 1

CONCLUSION:

The micro-grid based on small-hydro can work normally without disturbance by simulating the grid-connected operation and islanded operation. The power quality would have been improved when the micro-grid connected to the grid by comparing the waveforms of output voltage and active power assumption. And the THD would have decreased when the micro grid is in grid-connected operation. Analyze the recovering time and influence of fault-cutting time by setting fault to the micro-grid and grid. The simulation results stress the importance of fault-cutting time. Cutting off the fault in time would suppress the system oscillation, and the generators are easier to get synchronous again. The system would oscillate fiercely with high frequency if the fault could not be cut off in time. However, the actual situation is more complex. Considering the change of load, actual situation of small-hydro power plants (changes of water level and so on), development of different distributing power and so on, the structure of the conventional micro-grid will become more complex, so the model in the paper needs some improvement.

 REFERENCES:

[1] Tao YU,Haihua LIANG. “Smart power generation control for microgrids islanded operation based on reinforcement leaning”,. Master's degree thesis of south china university of technoiogy,2012

[2] Fred H. Schwartz, Mohammad Shahidehpour. “Small Hydro As Green Power.” Power Engineering Society General Meeting, USA, 2005, pp. 2050 - 2057.

[3] ZHANG YuanSheng, et al. “The effects on the load model of the distributed network with small hydro power.” 2011 The International Conference on Advanced Power System Automation and Protection, China, 2011, pp.911-916.

[4] Anuradha Wijesinghe, Loi Lei. “Small Hydro Power Plant Analysis and Development,” Electric Utility Deregulation and Restructuring and Power Technologies (DRPT), China, 2011, pp.25 –30.

[5] Guillermo C. Zu˜niga-Neria, Fernando Ornelas-Tellez,J. Jesus Rico. “Optimal Operation of Energy Resources in a Micro-grid.” Power Systems Conference, USA, 2014, pp. 1-6.

A Modified SEPIC Converter with High Static Gain for Renewable Applications

ABSTRACT:

Two high static gain step-up dc–dc converters based on the modified SEPIC converter are presented in this paper. The proposed topologies present low switch voltage and high efficiency for low input voltage and high output voltage applications. The configurations with magnetic coupling and without magnetic coupling are presented and analyzed. The magnetic coupling allows the increase of the static gain maintaining a reduced switch voltage. The theoretical analysis and experimental results show that both structures are suitable for high static gain applications as a renewable power sources with low dc output voltage. Two experimental prototypes were developed with an input voltage equal to 15 V and an output power equal to 100 W. The efficiency at nominal power obtained with the prototype without magnetic coupling was equal to 91.9% with an output voltage of 150 V. The prototype with magnetic coupling operating with an output voltage equal to 300 V, presents an efficiency at nominal power equal to 92.2%.

KEYWORDS:

1.      DC–DC power conversion

2.       Voltage multiplier and solar power generation

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

  CIRCUIT DIAGRAM:

 EXPECTED SIMULATION RESULTS:

CONCLUSION:

Two new topologies of non isolated high static gain converters are presented in this paper. The first topology without magnetic coupling can operate with a static gain higher than 10 with a reduced switch voltage. The structure with magnetic coupling can operate with static gain higher than 20 maintaining low the switch voltage. The efficiency of proposed converter without magnetic coupling is equal to 91.9% operating with input voltage equal to 15 V, output voltage equal 150 V, and output power equal 100 W. The efficiency of the proposed converter with magnetic coupling is equal to 92.2% operating with input voltage equal to 15V, output voltage equal 300V, and output power equal 100W. The commutation losses of the proposed converter with magnetic coupling are reduced due to the presence of the transformer leakage inductance and the secondary voltage multiplier that operates as a nondissipative clamping circuit to the output diode voltage.

REFERENCES:

 [1] C. W. Li and X. He, “Review of non-isolated high step-up DC/DC converters in photovoltaic grid-connected applications,” IEEE Trans. Ind. Electron., vol. 58, no. 4, pp. 1239–1250, Apr. 2011.

[2] C. S. B. Kjaer, J. K. Pedersen, and F. Blaabjerg, “A review of singlephase grid-connected inverters for photovoltaic modules,” IEEE Trans. Ind. Appl., vol. 41, no. 5, pp. 1292–1306, Sep. 2005.

[3] D. Meneses, F. Blaabjerg, O. Garcia, and J. A. Cobos, “Review and comparison of step-up transformerless topologies for photovoltaic AC-Module application,” IEEE Trans. Power Electron., vol. 28, no. 6, pp. 2649–2663, Jun. 2013.

[4] D. Zhou, A. Pietkiewicz, and S. Cuk, “A Three-Switch high-voltage converter,” IEEE Trans. Power Electron., vol. 14, no. 1, pp. 177–183, Jan. 1999.

[5] M. Prudente, L. L. Pfitscher, G. Emmendoerfer, E. F. Romaneli, and R. Gules, “Voltage multiplier cells applied to non-isolated DC–DC converters,” IEEE Trans. Power Electron., vol. 23, no. 2, pp. 871–887, Mar. 2008.

Sensorless Speed Estimation and Vector control of an Induction Motor drive Using Model Reference Adaptive Control

ABSTRACT:

Now-a-days, sensorless speed control modes of operation are becoming standard solutions in the area of electric drives. The technological developments require a compact and efficient drive to meet the challenging strategies in operation of the system. This paper provides a speed sensorless control of an Induction motor with a model based adaptive controller with stator current vectors. The purpose of the proposed control scheme is to create an algorithm that will make it possible to control induction motors without sensors. A closed loop estimation of the system with robustness against parameter variation is used for the control approach. A Model Reference Adaptive System (MRAS) is one of the major approaches used for adaptive control. The MRAS provides relatively easy implementation with a higher speed adaptation algorithm. MRAS proposed in this paper owing to its low complexity and less computational effort proposes a feasible methodology to control the speed of an Induction Motor (1M) drive without using speed sensors. Simulations results validate the effectiveness of this technique.

KEYWORDS:

1.      Indirect Field oriented control

2.      Induction motor drive

3.      Sensorless speed estimation

4.      Model Reference Adaptive control.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Proposed Block Diagram of MRAS based 1M drive using PI controller.

 SIMULINK MODEL:

Fig.2. Overall Simulink model of sensorless control of induction motor using MRAS with PI controller.

EXPECTED SIMULATION RESULTS:

CONCLUSION:

The model based control scheme is basically an adaptive control mechanism. The reference model of the proposed system consists of the response to be obtained for the input conditions. The adaptive mechanism continuously monitors the adaptable parameter (speed in this case). The

adaptable parameter is continuously subjected to changes based on its deviation obtained by comparing it with the response of the reference model. The speed estimation algorithm in MRAS is computationally less intensive. MRAS is a relatively simple algorithm and hence less sophisticated processing can be employed. MRAS strategy is more robust than the conventional one. This makes it better suited if the drive is to be operated in hostile environments. Owing to less sophisticated processing requirements, MRAS technique costs cheaper and hence overall cost of the drive is reduced. With lower cost and greater reliability without mounting problems, the sensorless vector control schemes have made remarkable developments in electric drive technology. Due to lesser rise time taken by MRAS, this method gives faster steady state response and this scheme has better reliability than the conventional scheme.

REFERENCES:

[I] Teresa Orlowska - Kowalska and Mateusz Dybkowski , "Stator Current based MRAS estimator for a wide range speed Sensor less induction motor drives", IEEE Transactions on Industrial Electronics vo1.51, No. 4, April 2010, pp. 1296 - 1308.

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

[3] M. Rodic and K. Jezernik, "Speed-sensorless sliding-mode torque control of induction motor," IEEE Transactions on Industrial Electronics, vol. 49, no. I, pp. 87-95, February 2002.

[4] L. Harnefors, M. Jansson, R. Ottersten and K. Pietilainen, "Unified sensorless vector control of synchronous and induction motors," IEEE Transactions on Industrial Electronics, vol. 50, no.

1, pp. 153-160, February 2003.

[5] M. Comanescu and L. Xu, "An improved flux observer based on PLL frequency estimator for sensorless vector control of induction motors," IEEE Transactions on Industrial Electronics, vol. 53, no. 1, pp. 50-56, February 2006.