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.

Power Quality Improvement of Unbalanced Power System with Distributed Generation Units

Power Quality Improvement of Unbalanced Power System with

Distributed Generation Units

ABSTRACT:

This paper presents a power electronic system for improving the power quality of the unbalanced distributed generation units in three-phase four-wire system. In the system, small renewable power generation units, such as small PV generator, small wind turbines may be configured as single phase generation units. The random nature of renewable power sources may result in significant unbalance in the power network and affect the power quality. An electronic converter system is proposed to correct the system unbalance and harmonics so as to deal with the power quality problems. The operation and control of the converter are described. Simulation results have demonstrated that the system can effectively correct the unbalance and enhance the system power quality.

KEYWORDS:

1.      Component

2.      Distributed generation

3.      Voltage source converter

4.      Power Quality Compensator

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Instantaneous power relationship in a system and a parallel connected compensator with energy storage system

Fig.2.The connection of VSC in a three-phase four-wire system

EXPECTED SIMULATION RESULTS:

Fig.3. Feeder 1 currents and power

 

Fig.4. Feeder 2 currents and power

Fig.5. Grid currents and power

                      

Fig.6. Compensator currents and power

                     

Fig.7. Grid current fundamental component

CONCLUSION:

This paper presents a study of using a voltage source converter (VSC) based compensator to deal with the unbalance and harmonic distortion issue in the low voltage system with embedded single phase DG units. The VSC performs the functions of an interface for an energy storage system as well. The VSC is connected in parallel with the system to control the energy storage system, correct the system unbalance, remove the harmonic components and minimize the neutral current of the supply system.

REFERENCES:

[1] G..Strbac, “Impact of dispersed generation on distribution systems: a European perspective” Power Engineering Society Winter Meeting, 2002. IEEE, vol. 1, . 2002, pp. 118 –120.

[2] M. Dussart, P. Lauwers, S. Magnus, Y. Laperches, “Connection requirements for dispersed generation: evolutions of existing requirements and need for further standardization” Electricity Distribution, 2001. Part 1: Contributions. CIRED2001, Conference Publication No. 482, © IEE2001

[3] J.A.P. Lopes, “Integration of dispersed generation on distribution networks-impact studies” Power Engineering Society Winter Meeting, 2002. IEEE, vol. 1, 2002, pp. 323 –328.

[4] F. Blaabjerg, Z. Chen, S. B Kjaer, “Power Electronics as Efficient Interface in Dispersed Power Generation Systems”, IEEE Transactions on Power Electronics, vol. 19, Issue: 5, Sept. 2004, pp.1184- 1194.

[5] Z. Chen, “Three Phase Four Wire System Power Redistribution Using A Power Electronic Converter”, Power Engineering Letters, IEEE Power Eng. Rev. October, 2000, pp. 47-49.

Transient Stability Enhancement by DSSC with Fuzzy Supplementary Controller

Transient Stability Enhancement by DSSC with

Fuzzy Supplementary Controller

ABSTRACT

 The distributed flexible alternative current transmission system (D-FACTS) is a recently developed FACTS technology. Distributed Static Series Compensator (DSSC) is one example of DFACTS devices. DSSC functions in the same way as a Static Synchronous Series Compensator (SSSC), but is smaller in size, lower in price, and possesses more capabilities. Likewise, DSSC lies in transmission lines in a distributed manner. In this work, we designed a fuzzy logic controller to use the DSSC for enhancing transient stability in a two-machine, two-area power system. The parameters of the fuzzy logic controller are varied widely by a suitable choice of membership function and parameters in the rule base. Simulation results demonstrate the effectiveness of the fuzzy controller for transient stability enhancement by DSSC.

KEYWORDS

1.      D-FACTS

2.       Simulation model

3.       DSSC

4.       Transient stability Fuzzy logic controller

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Simulation model of two-machine system for transient stability study with DSSC.

Fig. 2. D-FACTS deployed on the power line.

Fig. 3. Circuit schematic of a DSSC module.

EXPECTED SIMULATION RESULTS:

Fig. 4. Changing the rotor angle difference (d_theta1_2) when the DSSCs entered the circuit.

             

Fig. 5. Changing the rotor angle difference (d_theta1_2) after the fault with DSSC (without supplementary fuzzy logic damping controller) and without DSSC.

 Fig. 6. Changing the angular speed of the machines after the fault with DSSC (without supplementary fuzzy logic damping controller) and without DSSC.

Fig.7. Rotor angle difference (d_theta1_2) deviation after the fault with FLC and classic controller.

Fig. 8. Machine voltage variation after the fault with FLC and classic controller.

Fig. 9. Rotor angle difference (d_theta1_2) deviation after the fault with FLC and classic damping controller and without damping controller.

Fig. 10. Machine voltage variation after the fault with FLC and classic damping controller and without damping controller.

Fig. 11. Variation of FLC output signal after the fault.

CONCLUSION:

In this study, we introduced a graphical-based simulation model of the DSSC. DSSC was placed in a sample two machine power system to increase transient stability. Simulation studies presented in the paper showed that when the DSSCs were out of service, the rotor angle between the machines (d_theta1_2) increased rapidly and two machines fell out of synchronism after fault clearing. However, when the DSSCs were in circuit, DSSCs stabilized the system even without specific controller. Subsequently, an FLC was added to the main control system of the DSSC in order to improve the transient stability margin of the system. The simulation results show that specific to this case, DSSC can stabilize the system under severe fault. Moreover, a comparative study between the FLC and conventional classic controller shows that the proposed FLC has better performance and influence in transient stability enhancement and oscillation damping

REFERENCES:

[1] Yi Guo, David J. Hil and Youyi Wang, “Global Transient Stability and Voltage Regulation for Power System,” IEEE Transaction On Power System, Vol. 16, No. 4, Nov. 2001.

[2] L. Gyugyi, “Dynamic compensation of ac transmission lines by solid-state synchronous voltage sources,” IEEE Trans. Power Delivery, 19(2), 1994, pp.904-911.

[3] P. Rao, M.L. Crow and Z.Young, “STATCOM control for power system voltage control application,” IEEE Trans. Power Delivery, 15, 2000, pp.1311-1317.

[4] H. Wang and F.Li, “Multivariable sampled regulators for the coordinated control of STATCOM ac and dc voltage,” IEE Proc. Gen. Tran. Dist., 147(2), 2000, pp. 93-98.

[5] A.H.M.A Rahim and M.F.Kandlawala, “Robust STATCOM voltage controller design using loop shaping technique,” Electric Power System Research, 68, 2004, pp.61-74.

Seventeen-Level Inverter Formed by Cascading Flying Capacitor and Floating Capacitor H-Bridges

Seventeen-Level Inverter Formed by Cascading

Flying Capacitor and Floating Capacitor H-Bridges

ABSTRACT:

A multilevel inverter for generating 17 voltage levels using a three-level flying capacitor inverter and cascaded H-bridge modules with floating capacitors has been proposed. Various aspects of the proposed inverter like capacitor voltage balancing have been presented in the present paper. Experimental results are presented to study the performance of the proposed converter. The stability of the capacitor balancing algorithm has been verified both during transients and steady state operation. All the capacitors in this circuit can be balanced instantaneously by using one of the pole voltage combinations. Another advantage of this topology is its ability to generate all the voltages from a single dc-link power supply which enables back-to-back operation of converter. Also, the proposed inverter can be operated at all load power factors and modulation indices. Additional advantage is, if one of the H-bridges fail, the inverter can still be operated at full load with reduced number of levels. This configuration has very low dv/dt and common-mode voltage variation.

KEYWORDS:

1.     Cascaded H-bridge

2.     Flying capacitor

3.     Multilevel inverter

4.     17-level inverter.

                                          

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT  DIAGRAM:

CONCLUSION:

A new 17-level inverter configuration formed by cascading a three-level flying capacitor and three floating capacitor Hbridges has been proposed for the first time. The voltages of each of the capacitors are controlled instantaneously in few switching cycles at all loads and power factors obtaining high performance output voltages and currents. The proposed configuration uses a single dc link and derives the other voltage levels from it. This enables back-to-back converter operation where power can be drawn and supplied to the grid at prescribed power factor. Also, the proposed 17-level inverter has improved reliability. In case of failure of one of the H-bridges, the inverter can still be operated with reduced number of levels supplying full power to the load. This feature enables it to be used in critical applications like marine propulsion and traction where reliability is of highest concern. Another advantage of the proposed configuration is modularity and symmetry in structure which enables the inverter to be extended to more number of phases like five-phase and six-phase configurations with the same control scheme. The proposed inverter is analyzed and its performance is experimentally verified for various modulation indices and load currents by running a three-phase 3-kW 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] J. Rodriguez, J.-S. Lai, and F. Z. Peng, “Multilevel inverters: A survey of topologies, controls, and applications,” IEEE Trans. Ind. Appl., vol. 49, no. 4, pp. 724–738, Aug. 2002.

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

[3] 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.

[4] A. M. Massoud, S. Ahmed, P. N. Enjeti, and B. W.Williams, “Evaluation of a multilevel cascaded-type dynamic voltage restorer employing discontinuous space vector modulation,” IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 2398–2410, Jul. 2010.

[5] S. Rivera, S. Kouro, B.Wu, S. Alepuz,M. Malinowski, P. Cortes, and J. R. Rodriguez, “Multilevel direct power control—a generalized approach for grid-tied multilevel converter applications,” IEEE Trans. Power Electron., vol. 29, no. 10, pp. 5592–5604, Oct. 2014.