Direct Power Control Of Series Converter Of Unified Power-Flow Controller With Three-Level Neutral Point Clamped Converter

Direct Power Control Of Series Converter Of Unified Power-Flow Controller With Three-Level Neutral Point Clamped Converter

ABSTRACT:

A unified power-flow controller (UPFC) can enforce unnatural power flows in a transmission grid, to maximize the power flow while maintaining stability. Theoretically, active and reactive power flow can be controlled without overshoot or cross coupling. This paper develops direct power control, based on instantaneous power theory, to apply the full potential of the power converter. Simulation and experimental results of a full three-phase model with non ideal transformers, series multilevel converter, and load confirm minimal control delay, no overshoot nor cross coupling. A comparison with other controllers demonstrates better response under balanced and unbalanced conditions. Direct power control is a valuable control technique for a UPFC, and the presented controller can be used with any topology of voltage-source converters. In this paper, the direct power control is demonstrated in detail for a third-level neutral point clamped converter.

KEYWORDS:

1.      Direct power control

2.       Flexible ac transmission control (FACTS)

3.       Multilevel converter

4.       Sliding mode control

5.       Unified power-flow controller (UPFC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1.Laboratory setup.

 CONCLUSION:

The DPC technique was applied to a UPFC to control the power flow on a transmission line. The technique has been described in detail and applied to a three-level NPC converter. The main benefits of the control technique are fast dynamic control behavior with no cross coupling or overshoot, with a simple controller, independent of nodal voltage changes. The realization was demonstrated by simulation and experimental results on a scaled model of a transmission line. The controller was compared to two other controllers under balanced and unbalanced conditions, and demonstrated better performance, with shorter settling times, no overshoot, and indifference to voltage unbalance. We conclude that direct power control is an effective method that can be used with UPFC. It is readily adaptable to other converter types than the three-level converter demonstrated in this paper.

REFERENCES:

 [1] L. Gyugyi, “Unified power-flow control concept for flexible ac transmission systems,” Proc. Inst. Elect. Eng., Gen., Transm. Distrib., vol. 139, no. 4, pp. 323–331, Jul. 1992.

[2] L. Gyugyi, C. Schauder, S.Williams, T. Rietman, D. Torgerson, and A. Edris, “The unified power flow controller: A new approach to power transmission control,” IEEE Trans. Power Del., vol. 10, no. 2, pp. 1085–1097, Apr. 1995.

[3] X. Lombard and P. Therond, “Control of unified power flow controller: Comparison of methods on the basis of a detailed numerical model,” IEEE Trans. Power Syst., vol. 12, no. 2, pp. 824–830, May 1997.

[4] H. Wang, M. Jazaeri, and Y. Cao, “Operating modes and control interaction analysis of unified power flow controllers,” Proc. Inst. Elect. Eng., Gen., Transm. Distrib., vol. 152, no. 2, pp. 264–270, Mar. 2005.

[5] H. Fujita, H. Akagi, and Y. Watanabe, “Dynamic control and performance of a unified power flow controller for stabilizing an ac transmission system,” IEEE Trans. Power Electron., vol. 21, no. 4, pp. 1013–1020, Jul. 2006.

Speed Control of Separately Excited DC Motor

Speed Control of Separately Excited DC Motor

ABSTRACT:

This paper proposes the speed control of a separately excited dc motor varying armature voltage. The novelty of this paper lies in the application of nonlinear autoregressive-moving average L2 controller for the speed control of SEDM. This paper also discusses speed control of a SEDM using chopper circuit. The performance of the proposed system has been compared with the traditional one using conventional controllers. The entire system has been modeled using MATLAB 7.0 toolbox. It has been found that both PI and hysteresis current controllers could be eliminated by the use of NARMA-L2 controller.

KEYWORDS:

1.      Chopper Circuit

2.       NARMA-L2

3.       SEDM

4.       Speed control

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 Fig. 1: Speed control circuit of a separately excited dc motor

 CONCLUSION:

Speed controller system based on NARMA-L2 controller has been successfully developed using

MATLAB to control the speed of a separately excited dc motor. The novelty of this paper lies in the application of NARMA–L2 controller to control of a separately excited dc motor. This paper also discusses modeling and control of SEDM using Sim Power Systems and simulink models. The performance of the system has been compared using different types of controllers. It has been found that NARMA-L2 controller is able to regulate the speed well above the rated values.

REFERENCES:

1. Zuo Z. Liu, Fang L. Luo, and Muhammad H. Rasid, “High performance nonlinear MIMO field weakening controller of a separately excited dc motor,” Electric Power Systems Research, vol. 55, issue 3, Sep. 2000, pp. 157-164.

2. Nabil A. Ahmed, “Modeling and simulation of acdc buck-boost converter fed dc motor with uniform PWM technique,” Electric Power Systems Research, vol.73, issue 3, Mar. 2005, pp. 363-372.

3. J. Figueroa, C. Brocart, J. Cros, and P. Viarouge, “Simplified simulation methods for polyphase brushless DC motors,” Mathematics and Computers in Simulation, vol. 63, issues 3-5, Nov. 2003, pp. 209-224.

4. J. Santana, J. L. Naredo, F. Sandoval, I. Grout, and O. J. Argueta, “Simulation and construction of a speed control for a DC series motor,” Mechatronics, vol. 12, issues 9-10, Nov.-Dec. 2002, pp. 1145-1156.

5. Charles I. Ume, John Ward, and Jay Amos, “Application of MC68HC11 microcontroller for speed control of a DC motor,” Journal of Microcomputer Applications, vol. 15, issue 4, Oct. 1992, pp. 375-385. 

STATCOM for Improved Dynamic Performance of Wind Farms in Power Grid

              STATCOM for Improved Dynamic Performance of Wind

Farms in Power Grid

ABSTRACT:

Application of FACTS controller called Static Synchronous Compensator STATCOM to improve the performance of power grid with Wind Farms is investigated .The essential feature of the STATCOM is that it has the ability to absorb or inject fastly the reactive power with power grid . Therefore the voltage regulation of the power grid with STATCOM FACTS device is achieved. Moreover restoring the stability of the power system having wind farm after occurring severe disturbance such as faults or wind farm mechanical power variation is obtained with STATCOM controller . The dynamic model of the power system having wind farm controlled by proposed STATCOM is developed . To Validate the powerful of the STATCOM FACTS controller , the studied power system is simulated and subjected to different severe disturbances . The results prove the effectiveness of the proposed STATCOM controller in terms of fast damping the power system oscillations and restoring the power system stability .

KEYWORDS:

1.      STATCOM

2.       Wind Generation

3.       Transient Stability

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Studied model

 CONCLUSION:

Power system with wind farms performance can be improved using FACTS devices such as STATCOM . The dynamic model of the studied power system is simulated using Simulink Matlab package sofware . To validate the effect of the STATCOM controller of power system operation , the system is subjected to different disturbances such as faults and power operating conditions . The digital results prove the powerful of the proposed STATCOM controller in terms of Stability improvement, power swings damping, voltage regulation, increase of power transmission and chiefly as a supplier of controllable reactive power to accelerate voltage recovery after fault occurrence.

 REFERENCES:

 [1] V. Akhmatov, H.knudsen, A.H. Nielsen, J.K.pedersen, and N.K. poulsen, "A dynamic stability limit of grid connected induction generators", Pro. International IASTED conference on power and energy systems, marbella, spain, 2000.

[2] L. holdsworth, X.G. Wu, J.B. EKanayake, and N. Jenkins, "Comparison of fixed-speed and doubly-fed induction generator wind turbines during power system disturbances", IEE proc. C-Gener. Transm. Distrib., vol. 150, no. 3, pp. 343-352, 2003.

[3] S.M. Bolik, "Grid requirments challenges for wind turbines", Fourth International Workshop on large-scale Integration of Wind Power and transmission networks for Offshore Wind Farms, Oct .2003.

[4] L. Holdsworth, N.Jenkins, and G. Strbac, "Electrical stability of large, offshore wind farms", IEE seventh International Conference on AC-DC power Transmission, pp.156-161-2001.

[5] X.G. Wu, A.Arulampalam, C. Zhan, and N.jenkins, "Application of a static reactive power compensator (STATCOM) and a dynamic braking resistor (DBR) for the stability enhancement of a large wind farms", Wind Engineering Journal, vol. 27, no.2, pp.93-106, March2003.

Direct Torque Control Based on Space Vector Modulation with Adaptive Stator Flux Observer for Induction Motors

Direct Torque Control Based on Space Vector Modulation with Adaptive Stator Flux Observer for Induction Motors

ABSTRACT:

 This paper describes a combination of direct torque control (DTC) and space vector modulation (SVM) for an adjustable speed sensor less induction motor (IM) drive. The motor drive is supplied by a two-level SVPWM inverter. Using the IM model in the stator – axes reference frame with stator current and flux vectors components as state variables. In this paper, a conventional PI controller is designed accordingly for DTC-SVM system. Moreover, a robust full-order adaptive stator flux observer is designed for a speed sensor less DTC-SVM system and a new speed adaptive law is given. By designing the observer gain matrix based on state feedback control theory, the stability and robustness of the observer systems is ensured. Finally, the effectiveness and validity of the proposed control approach is verified by simulation results.

KEYWORDS:

1.     DTC

2.      Stator Flux Observer

3.     Torque Ripple

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 Fig. 1 Block Diagram of DTC-SVM system

 CONCLUSION:

A novel DTC-SVM scheme has been developed for the IM drive system, In this control method, a SVPWM inverter is used to feed the motor, the stator voltage vector is obtained to fully compensate the stator flux and torque errors. Furthermore, a robust full-order adaptive flux observer is designed for a speed sensor-less DTC-SVM system. The stator flux and speed are estimated synchronously. By designing the constant observer gain matrix, the robustness and based on state feedback stability of the observer systems is ensured. Therefore, the proposed sensor-less drive system is capable of steadily working in very low speed, has much smaller torque ripple and exhibits good dynamic and steady-state performance.

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, 1986.

[2] Y. S. Lai and J. H. Chen, “A new approach to direct torque control ofinduction motor drives for constant inverter switching frequency andtorque ripple reduction,” IEEE Trans. Energy Convers., vol. 16, no. 3,pp. 220–227, 2001.

 [3] S. Mir, M. E. Elbuluk, and D. S. Zinger, “PI and fuzzy estimators for tuning the stator resistance in direct torque control of induction machines,” IEEE Trans. Power Electron., vol. 13, no. 2, pp. 279–287,1998.

[4] F. Bacha, R. Dhifaoui, and H. Buyse, “Real-time implementation ofdirect torque control of an induction machine by fuzzy logic controller,” in Proc. ICEMS, 2001, vol. 2, pp. 1244–1249.

[5] A. Arias, J. L. Romeral, and E. Aldabas, “Fuzzy logic direct torquecontrol,” in Proc. IEEE ISIE, 2000, vol. 1, pp. 253–258.

Simulation and Analysis of Zero Voltage Switching PWM Full Bridge Converter

Simulation and Analysis of Zero Voltage Switching PWM Full Bridge Converter

ABSTRACT:

In the conventional zero voltage switching full bridge converter the introduction of a resonant inductance and clamping diodes are introduced the voltage oscillation across the rectifier diodes is eliminated and the load range for zero-voltage switching (ZVS) achievement increases. When the clamping diode is conducting, the resonant inductance is shorted and its current keeps constant. So the clamping diode is hard turned-off, leading to reverse recovery loss if the output filter inductance is relatively larger. By introducing a reset winding in series with the resonant inductance to make the clamping diode current decay rapidly when it conducts this paper improves the full-bridge converter. The conduction losses are reduced by the use of reset winding. Also the clamping diodes naturally turn-off and avoids the reverse recovery. The proposed converter has been simulated for two different configurations and results have been compared. A 1 kW prototype converter is built to verify the operation principle and the experimental results are also demonstrated.

KEYWORDS:

1.      Clamping diodes

2.       full bridge converter

3.       Reset winding

4.       zero-voltage-switching (ZVS)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

 Fig: 1. Transformer-lag type ZVS PWM full bridge converter

Fig: 2. Transformer-lead type ZVS PWM full bridge converter

 CONCLUSION:

A ZVS PWM full-bridge converter is proposed in this paper, it employs an additional reset winding to make the clamping diode current decay rapidly when the clamping diode conducts, thus the conduction losses of the clamping diodes. The reset winding removes the need of auxiliary switches and the resonant inductance is reduced. The use of reset winding removes the need of hard switching for clamping diodes so there will not be any power loss due to switching of clamping diodes and the conversion efficiency will increased. In the meanwhile, the clamping diodes can be turned off naturally without reverse recovery over the whole input voltage range, and the output filter inductance can be designed to be large to obtain small current ripple, leading to reduced filter capacitance. Compared with the traditional full bridge converter, the proposed circuit provides another simple and effective approach to avoid the reverse recovery of the clamping diodes. The structure and operation of the proposed ZVS PWM full-bridge converter with reset winding topology are described and two configurations have been studied i.e. Transformer leading and Transformer-Lagging connections. We have studied the performance of both the configuration. If we compare the rectifier output in both the case we find that Tr-Lag connection produces less ripples. Transformer lagging configuration is advisable for more accurate results.

REFERENCES:

 [1] B.P. Mcgrath, D.G. Holmes, McGoldrick and A.D. Mclve, “Design of a soft-switched 6-kW battery charger for traction applications,” IEEE Trans. Power Electron, vol.22,no. 4, pp. 1136-1144, Jull. 2007.

[2] J. Dudrick, P. Spanik and N.D. Trip, “Zero-voltage and zero-current switching full-bridge dc-dc converter with auxiliary transformer,” IEEE Trans. Power Electron, vol.21, no.5, pp.1328-1335, Sep. 2006.

[3] J.Zhang, X. Xie, X. Wu, G. Wu and Z. Qian, “ A novel zero-current transition full bridge dc-dc converter,” IEEE Trans. Power Electron, vol. 21, no. 2, pp. 354-360, Mar. 2006.

[4] Darlwoo Lee, Taeyoung Abu, Byungcho Choi, “A new soft switching dc-to-dc converter employing two transformer”, . PESC, pp. 1-7, June 2006.

[5] Xinyu Xu Ashwin M. Khambadkhone, Toh Meng Leong, Ramesh Oruganti, “ A 1 MHz zero-voltage switching asymmetrical half bridge dc/dc converter: analysis and design” IEEE Trans. Power Electron, vol.21, no. 1, pp. 105-113, Jan. 2006.

High-Step-Up and High-Efficiency Fuel-Cell Power-Generation System With Active-Clamp Flyback–Forward Converter

High-Step-Up and High-Efficiency Fuel-Cell Power-Generation System With Active-Clamp Flyback–Forward Converter

ABSTRACT:

A high-efficiency fuel-cell power-generation system with an active-clamp flyback–forward converter is presented in this paper to boost a 12-V dc voltage into a 220-V 50-Hz ac voltage. The proposed system includes a high-efficiency high-step-up interleaved soft-switching flyback–forward converter and a full-bridge inverter. The front-end active-clamp flyback–forward converter has the advantages of zero-voltage-switching performance for all the primary switches, reverse-recovery-problem alleviation for the secondary output diodes, large voltage-conversion ratio, and small input-current ripple. Furthermore, there are two coupled inductors in the proposed converter. Each coupled inductor can work in the flyback mode when the corresponding main switch is in the turn-on state and in the forward mode when it is in the turnoff state, which takes full use of the magnetic core and improves the power density. In addition, the full-bridge inverter with an LC low-pass filter is adopted to provide low-total-harmonic-distortion ac voltage to the load. Therefore, high-efficiency and high-power density conversion can be achieved in a wide input-voltage range by employing the proposed system. Finally, a 500-W prototype and another 1-kW converter are implemented and tested to verify the effectiveness of the proposed system.

 KEYWORDS:

1.      Active clamp

2.       Fly back–forward converter

3.       Fuel cell generation system.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Proposed high-efficiency fuel-cell power-generation system

CONCLUSION:

In this paper, an interleaved high-step-up ZVS flyback– forward converter has been proposed for the fuel-cell power generation system. The voltage doubler rectifier structure is employed to provide a large voltage-conversion ratio and to remove the output-diode reverse-recovery problem. Furthermore, ZVS soft-switching operation is realized for all the primary active switches to minimize the switching losses. In addition, the input-current ripple is small due to the interleaved operation and the current-fed-type configuration. The steady state operation analysis and the main circuit performance are discussed to explore the advantages of the proposed converter in a high-efficiency high-step-up power-generation system. Finally, a 500-W 12-V dc to 220-V ac system is employed and another 1-kW prototype operated at 100 kHz is tested as examples to illustrate the important design guidelines of the proposed converter. Experimental results have demonstrated that the proposed system is an excellent power-converter system for fuel-cell applications, featuring high efficiency, high-step up ratio, and high power density.

REFERENCES:

[1] S. Jemei, D. Hissel, M. C. Pera, and J. M. Kauffmann, “A new modeling approach of embedded fuel-cell power generators based on artificial neural network,” IEEE Trans. Ind. Electron., vol. 55, no. 1, pp. 437–447, Jan. 2008.

[2] M. H. Todorovic, L. Palma, and P. N. Enjeti, “Design of a wide input range dc–dc converter with a robust power control scheme suitable for fuel cell power conversion,” IEEE Trans. Ind. Electron., vol. 55, no. 3, pp. 1247–1255, Mar. 2008.

[3] K. Jin,M. Yang, X. Ruan, and M. Xu, “Three-level bidirectional converter for fuel-cell/battery hybrid power system,” IEEE Trans. Ind. Electron., vol. 57, no. 6, pp. 1976–1986, Jun. 2010.

[4] C. T. Pan and C. M. Lai, “A high-efficiency high step-up converter with low switch voltage stress for fuel-cell system applications,” IEEE Trans. Power Electron., vol. 57, no. 6, pp. 1998–2006, Jun. 2010.

[5] E. H. Kim and B. H. Kwon, “Zero-voltage- and zero-current-switching full-bridge converter with secondary resonance,” IEEE Trans. Ind. Electron., vol. 57, no. 3, pp. 1017–1025, Mar. 2010.

Dynamic Modeling of Microgrid for Grid Connected and Intentional Islanding Operation

Dynamic Modeling of Microgrid for Grid Connected and Intentional Islanding Operation

ABSTRACT:

Microgrid is defined as the cluster of multiple distributed generators (DGs) such as renewable energy sources that supply electrical energy. The connection of microgrid is in parallel with the main grid. When microgrid is isolated from remainder of the utility system, it is said to be in intentional islanding mode. In this mode, DG inverter system operates in voltage control mode to provide constant voltage to the local load. During grid connected mode, the Microgrid operates in constant current control mode to supply preset power to the main grid. The main contribution of this paper is summarized as

1) Design of a network based control scheme for inverter based sources, which provides proper current control during grid connected mode and voltage control during islanding mode.

2) Development of an algorithm for intentional islanding detection and synchronization controller required during grid reconnection.

3) Dynamic modeling and simulation are conducted to show system behavior under proposed method using SIMULINK.

From the simulation results using Simulink dynamic models, it can be shown that these controllers provide the microgrid with a deterministic and reliable connection to the grid.

KEYWORDS:

1.      Distributed generation (DG)

2.       grid connected operation

3.       intentional islanding operation and islanding detection

4.       Microgrid

5.       Synchronization

6.       voltage source converter (VSC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Dynamic model of microgrid with controller.

CONCLUSION:

Current and voltage Control techniques have been developed for grid connected and intentional islanding modes of operation using PI controllers. An intentional islanding detection algorithm responsible for switching between current control and voltage control is developed using logical operations and proved to be effective. The reconnection algorithm coupled with the synchronization controller enabled the DG to synchronize itself with the grid during grid reconnection. The performance of the microgrid with the proposed controllers and algorithms has been analyzed by conducting simulation on dynamic model using SIMULINK. The simulation results presented here confirms the effectiveness of the control scheme.

REFERENCES:

[1] L. Shi, M.Y. Lin Chew. “A review on sustainable design of renewable energy systems,” science direct journal present in Renewable and Sustainable Energy Reviews, Vol. 16, Issue 1, 2012, pp. 192–207.

[2] Q. Lei, Fang Zheng Peng, Shuitao Yang. “Multi loop control method for high performance microgrid inverter through load voltage and current decoupling with only output voltage feedback,” IEEE Trans. power. Electron, vol. 26, no. 3, 2011, pp. 953–960.

[3] J. Selvaraj and N. A. Rahim, “Multilevel inverter for grid-connected PV system employing digital PI controller,” IEEE Trans. Ind. Electron., vol. 56, no. 1, 2009, pp. 149–158.

[4] I. J. Balaguer, Fang Zheng Peng, Shuitao Yang, Uthane Supatti Qin Lei. “Control for grid connected and intentional islanding modes of operations of distributed power generation,” IEEE Trans. Ind. Electron., vol. 56, no. 3, 2009, pp. 726–736.

[5] R. J. Azevedo, G.I. Candela, R. Teodorescu, P.Rodriguez , I.E-Otadui “Microgrid connection management based on an intelligent connection agent,” 36th annual conference on IEEE industrial electronics society, 2010, pp. 3028–3033.