Convertible Unified Power Quality Conditioner to mitigate voltage and current imperfections

 ABSTRACT

This paper proposes a novel convertible unified power quality conditioner (CUPQC) by employing three voltage source converters (VSCs) which are connected to a multi-bus/multifeeder distribution system to mitigate current and voltage imperfections. The control performance of the VSCs is characterized by a minimum of six circuit open/close switches configurable in a minimum of seventeen combinations to enable the CUPQC to operate as shunt and series active power filters (APFs), unified power quality conditioner (UPQC), interline UPQC (IUPQC), multi-converter UPQC (MC-UPQC) and generalized UPQC (GUPQC). The simulation and compensation performance analysis of CUPQC are based on PSCAD/EMTDC.

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM

Fig.1 Schematic representation of proposed CUPQC

EXPECTED SIMULATION RESULTS

Fig.2. Feeder1 (a) Load current (b) Source voltage

Fig.3. Feeder1 (a) Compensation currents (b) Compensation voltages

Fig.4. Feeder1 (a) Source currents (b) Load voltages

Fig.5. Feeder1 THD spectrum (a) Currents (b) Voltages

Fig.6. Feeder3 source voltage

Fig.7. Feeder3 compensation voltage

Fig.8. Feeder3 load voltages

Fig.9. Feeder3 voltage THD before and after compensation

Fig.10. (a) Feeder1source voltage (b) Feeder2 source voltage (c) Feeder3 load

current

Fig.11. (a) Feeder1 compensation voltages (b) Feeder2 compensation

voltages(c) Feeder3 compensation currents

Fig.12. (a) Feeder1 load voltages (b) Feeder2 load voltages (c) Feeder3 source

Currents

Fig.13. THD before and after compensation (a) Feeder1 voltage (b) Feeder2

voltage (c) Feeder3 current

Fig.14. RMS voltage (a) Feeder1 (b) Feeder2

CONCLUSION

In this paper the performance of the proposed CUPQC in three modes of operation as UPQC, MC-UPQC and GUPQC on a multi-bus/multi-feeder distribution system is validated by simulation results. The operating modes of the novel power quality conditioner in 17 different modes for compensation of currents and voltage interruptions are clearly explained. As an extension to this analysis, the authors are working on a model for characterization and testing of the proposed CUPQC.

.

REFERENCES

[1] H. Akagi, and H. Fujita “A new power line conditioner for harmonic compensation in power systems,” IEEE Trans. Power Del., vol. 10, 1995.

[2] P. Mitra, and G. Kumar, “An adaptive control strategy for DSTATCOM applications in an electric ship power system,” IEEE Trans. Power Electro., vol. 25, no. 1, pp. 95 –104, Jan. 2010.

[3] M. J. Newman, D. G. Holmes, J. G. Nielsen, and F. Blaabjerg, “A dynamic voltage restorer (DVR) with selective harmonic compensation at medium voltage level” IEEE Trans. Ind. Appl., vol. 41, no. 6, pp. 1744 – 1753, Nov. 2005.

[4] H. Fujita, and H. Akagi, “The unified power quality conditioner: The integration of series and shunt-active filters,” IEEE Trans. Power Electron., vol. 13, no. 2, pp. 315 – 322, Mar. 1998.

[5] V. Khadkikar, and A. Chandra, “A novel structure for three-phase four wire distribution system utilizing unified power quality conditioner,” IEEE Trans. Ind. Appl., vol. 45, no. 5, pp. 1897 – 1902, Sept./Oct. 2009.

Control of a Small Wind Turbine in the High Wind Speed Region

ABSTRACT:

This paper proposes a new soft-stalling control strategy for grid-connected small wind turbines operating in the high and very high wind speed conditions. The proposed method is driven by the the rated current/torque limits of the electrical machine and/or the power converter, instead of the rated power of the connected load, which is the limiting factor in other methods. The developed strategy additionally deals with the problem of system startup preventing the generator from accelerating to an uncontrollable operating point under a high wind speed situation. This is accomplished using only voltage and current sensors, not being required direct measurements of the wind speed nor the generator speed. The proposed method is applied to a small wind turbine system consisting of a permanent magnet synchronous generator and a simple power converter topology. Simulation and experimental results are included to demonstrate the performance of the proposed method. The paper also shows the limitations of using the stator back-emf to estimate the rotor speed in permanent magnet synchronous generators connected to a rectifier, due to significant d-axis current at high load.

SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

Fig. 1. Schematic representation of the wind energy generation system: a) Wind turbine, generator and power converter; b) Block diagram of the boost converter control system; c) Block diagram of the H-bridge converter control system.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation result showing the behavior of the proposed method under increasing wind conditions (10 m/s, 17 m/s from 10 s, and 33 m/s from 13s): a) rectifier voltage command (v_ r ), rectifier voltage (vr) and minimum rectifier voltage command (v_ r min); b) boost current (ib), filtered boost current (~i

b), current limit (ilimit) and MPPT current target (imppt); c) turbine torque (Tt) and generator torque (Tg); d) mechanical rotor speed (!rm).

Fig. 3. Simulation result showing the behavior of the proposed method under decreasing wind conditions (30 m/s, 21 m/s from 4.5 s, and 8.5 m/s from 7s): a) rectifier voltage command (v_ r ), rectifier voltage (vr) and minimum rectifier voltage command (v_ r min); b) boost current (ib), filtered boost current (~I b), current limit (ilimit) and MPPT current target (imppt); c) turbine torque (Tt) and generator torque (Tg); d) mechanical rotor speed

(!rm).

Fig. 4. Experimental results showing the behavior of the propose method under increasing wind conditions (10 m/s, 17 m/s from 10 s, and 33 m/s from 13 s): a) rectifier voltage command (v_ r ), rectifier voltage (vr) and minimum rectifier voltage command (vr min); b) boost current (ib), filtered boost current (~I b), current limit (ilimit) and MPPT current target (imppt); c) mechanical rotor speed (!rm).

Fig. 5. Experimental results showing the behavior of the propose method under decreasing wind conditions (30 m/s, 21 m/s from 4.5 s, and 8.5 m/s from 9 s): a) rectifier voltage command (v_ r ), rectifier voltage (vr) and minimum rectifier voltage command (vr min); b) boost current (ib),filtered boost current (~I b), current limit (ilimit) and MPPT current target (imppt); c) mechanical rotor speed (!rm).

CONCLUSION:

The operation of small wind turbines for domestic or small business use is driven by two factors: cost and almost unsupervised operation. Specially important is the turbine operation and protection under high wind speeds, where the turbine torque can exceed the rated torque of the generator. This paper proposes a soft-stall method to decrease the turbine torque if a high wind speed arises and, as a unique feature, the method is able to early detect a high wind condition at startup keeping the turbine/generator running at low rotor speed avoiding successive start and stop cycles. The proposed method uses only voltage and current sensors typically found in small turbines making it an affordable solution. Both simulation and experimental results demonstrate the validity of the proposed concepts. This paper also shows that commonly used machine and rectifier models assuming unity power factor do not provide accurate estimations of the generator speed in loaded conditions, even if the resistive and inductive voltage drop are decoupled, due to the significant circulation of d-axis current if a PMSG is used. This paper proposes using a pre-commissioned look-up table whose inputs are both the rectifier output voltage and the boost current.

 REFERENCES:

[1] W. Kellogg, M. Nehrir, G. Venkataramanan, and V. Gerez, “Generation unit sizing and cost analysis for stand-alone wind, photovoltaic, and hybrid wind/PV systems,” IEEE Transactions on Energy Conversion, vol. 13, no. 1, pp. 70–75, Mar. 1998.

[2] P. Gipe, Wind Power: Renewable Energy for Home, Farm, and Business, 2nd Edition. Chelsea Green Publishing, Apr. 2004.

[3] A. C. Orrell, H. E. Rhoads-Weaver, L. T. Flowers, M. N. Gagne, B. H. Pro, and N. A. Foster, “2013 Distributed Wind Market Report,” Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Tech. Rep., 2014. [Online]. Available: http://www.osti.gov/scitech/biblio/1158500

[4] J. Benjanarasut and B. Neammanee, “The d-, q- axis control technique of single phase grid connected converter for wind turbines with MPPT and anti-islanding protection,” in 2011 8th International Conference on Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology (ECTI-CON). IEEE, May 2011, pp. 649–652.

[5] M. Arifujjaman, “Modeling, simulation and control of grid connected Permanent Magnet Generator (PMG)-based small wind energy conversion system,” in Electric Power and Energy Conference (EPEC), 2010 IEEE, Aug. 2010, pp. 1 –6.

Battery Energy Storage System for Variable Speed Driven PMSG for Wind Energy Conversion System

ABSTRACT:

There are many loads such as remote villages, islands, etc. that are located far away from the main grid. These loads require stand-alone generating system, which can provide constant voltage and frequency for local electrification. Locally available wind power can be used in such off-grid systems. As the wind speed is variable, an AC-DC-AC conversion system is required to convert variable voltage and variable frequency power generation to constant voltage and constant frequency source. Further, as the wind power as well as load is variable there is a need of energy storage device that take care of the load mismatch. In this paper, a standalone wind energy conversion system (WECS) using a variable speed permanent magnet synchronous generator (PMSG) is proposed with a battery energy storage system.

KEYWORDS:

1.      Wind energy conversion system

2.      Isolated system

3.      BESS

4.      Permanent magnet synchronous generator

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1 PMSG with PWM rectifier with battery for storing the extra wind energy

EXPECTED SIMULATION RESULTS:

Fig.2. Variation of wind speed, load voltages, load currents, generator power, battery power, load power battery current and DC link voltage.

CONCLUSION:

The isolated operation of wind energy conversion system requires AC-DC-AC interface with the capability of converting variable voltage variable frequency to constant voltage constant frequency source. In addition the power balancing has to be done with some energy storage system, According to the proposed topology, battery energy storage system provides power balance between the generated power and the load. The power mismatch is absorbed by the BESS.

REFERENCES:

[1] Bhim Singh and Gaurav Kumar Kasal, “Solid-State Voltage and Frequency Controller for a stand alone wind power generating system,” IEEE Trans. Power Electronics, vol. 23, no.3, pp.1170–1177, 2008.

[2] Bhim Singh and Gaurav Kumar Kasal, “Voltage and Frequency Controller for a 3-Phase 4-Wire Autonomous Wind Energy Conversion System” accepted for publication in IEEE Trans. on Energy Conversion.

[3] Ghosh and G. Ledwich, Power Quality Enhancement Using Custom Power Devices. Kulwer Academic, 2002.

[4] Gipe, P. Wind power’, Chelsea Green Publishing Company, Post Mills, Vermount, USA,1995.

[5] Rai, G.D. (2000) ‘Non conventional energy sources’, Khanna Publishers, 4th Edition, New Delhi (India)

An Energy Management Scheme with Power Limit Capability and an Adaptive Maximum Power Point Tracking for Small Standalone PMSG Wind Energy Systems

ABSTRACT:

Due to its high energy generation capability and minimal environmental impact, wind energy is an elegant solution to the growing global energy demand. However, frequent atmospheric changes make it difficult to effectively harness the energy in the wind because maximum power extraction occurs at a different operating point for each wind condition. This paper proposes a parameter independent intelligent power management controller that consists of a slope-assisted maximum power point tracking (MPPT) algorithm and a power limit search (PLS) algorithm for small standalone wind energy systems with permanent synchronous generators. Unlike the parameter independent perturb & observe (P&O) algorithms, the proposed slope-assisted MPPT algorithm preempts logical errors attributed to wind fluctuations by detecting and identifying atmospheric changes. The controller’s PLS is able to minimize the production of surplus energy to minimize the heat dissipation requirements of the energy release mechanism by cooperating with the state observer and using the slope parameter to seek the operating points that result in the desired power rather than the maximum power. The functionality of the proposed energy management control scheme for wind energy systems is verified through simulation results and experimental results.

KEYWORDS:

1.      Wind energy

2.       Maximum power point tracking

3.      Energy  management

4.      Power electronics

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig 1 System diagram with the proposed management control algorithm

EXPECTED SIMULATION RESULTS:

Fig 2 Performance of the standard fixed-step size P&O algorithm (average power captured = 1066 W).

Fig 3 Performance of the standard variable-step size P&O algorithm (average power captured = 1106 W).

Fig 4 Performance of the slope-assisted MPPT algorithm (1238 W).

Fig 5 Power coefficient performance of the fixed-step size P&O, variable step size P&O, and the slope assist MPPT (comparison performed under atmospheric identical conditions as depicted in Fig.20).

CONCLUSION:

In this paper, an intelligent parameter-independent power management controller has been presented for standalone offgrid small wind energy systems. With the state observer presiding over the slope-assisted MPPT and the PLS in the proposed controller, the convergence times to the desired operating points is reduced and the logical errors are minimized by identifying the changes in wind conditions. Being applicable for both grid-connected and standalone wind systems, the slope assist MPPT increases a wind system’s MPP search efficiency and enables the wind system to actively adapt to its changing behavior and wind conditions. The PLS algorithm was designed to complement the slope assist MPPT for standalone wind systems that have limited energy storage and use energy dissipation mechanisms to disperse surplus energy. Rather than focusing on capturing maximum power, the power limit search focuses on reducing the size and heat requirements of the energy dissipation mechanism by minimizing surplus power generation as desired. The operating principles of the proposed PLS and MPPT control techniques have been discussed in this paper. Simulation results on a 3kW system and experimental results on a proof-of-concept prototype with a wind turbine emulator have been provided to highlight the merits of this work.

REFERENCES:

[1] Global Wind Energy Council, "Global Wind Report - Anual Market Update 2012," 2013.

[2] Global Wind Energy Council, "Global Wind 2011 Report," 2012.

[3] Canadian Wind Energy Association, "Canadian Wind Energy Association," [Online]. Available: www.canwea.ca.

[4] Q. Wang and L. Chang, "An Intelligent Maximum Power Extraction Algorithm for Inverter-Based Variable Speed Wind Turbine Systems," IEEE Transactions on Power Electronics, vol. 1, September 2004, pp. 1242-1249.

[5] E. Koutroulis and K. Kalaitzakis, "Design of a Maximum Power Tracking System for Wind Energy Conversion Applications," IEEE Transaction on Industrial Electronics, vol. 53, no. 2, April 2006, pp. 486-494.

An Autonomous Wind Energy Conversion System with Permanent Magnet Synchronous Generator

ABSTRACT:

This paper deals with a permanent magnet synchronous generator (PMSG) based variable speed autonomous wind energy conversion system (AWECS). Back back connected voltage source converter (VSC) and a voltage source inverter (VSI) with a battery energy storage system (BESS) at the intermediate dc link are used to realize the voltage and frequency controller (VFC). The BESS is used for load leveling and to ensure the reliability of the supply to consumers connected at load bus under change in wind speed. The generator-side converter operated in vector control mode for achieving maximum power point tracking (MPPT) and to achieve unity power factor operation at PMSG terminals. The load-side converter is operated to regulate amplitude of the load voltage and frequency under change in load conditions. The three-phase four wire consumer loads are fed with a non-isolated star-delta transformer connected at the load bus to provide stable neutral terminal. The proposed AWECS is modeled, design and simulated using MATLAB R2007b simulink with its sim power system toolbox and discrete step solver.

KEYWORDS:

1.      Battery

2.      Permanent Magnet Synchronous Generator

3.      Star-delta Transformer

4.      Voltage Source Converters

5.      Maximum Power Point Tracking

6.      Wind Energy

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Proposed control scheme of VFC for PMSG based AWECS

 EXPECTED SIMULATION RESULTS:

Fig. 2 Performance of Controller during fall in wind speed

Fig. 3 Performance of Controller during rise in wind speed

Fig. 4 Performance of Controller at fixed wind speed and balanced/unbalanced non-linear loads

 CONCLUSION:

A new configuration of voltage and frequency controller for a permanent magnet synchronous generator based variable speed autonomous wind energy conversion system has been designed modeled and its performance is simulated. The VFC has used two back-back connected VSC’s and BESS at intermediate dc link. The GSC has been controlled in vector controlled to achieve MPPT, unity power factor operation of PMSG. The LSI has been controlled to maintain amplitude of load voltage and its frequency. The VFC has performed the function of a load leveler, a load balancer, and a harmonic eliminator.

REFERENCES:

[1] J. F. Gieras and M. Wing, Permanent Magnet Motor Technology – Design and Application, Marcel Dekker Inc., New York, 2002.

[2] M. Kimura, H. Koharagi, K. Imaie, S. Dodo, H. Arita and K. Tsubouchi, “A permanent magnet synchronous generator with variable speed input for co-generation system,” IEEE Power Engineering Society Winter Meeting, 2001, vol. 3, 28 Jan.-1 Feb. 2001, pp. 1419 – 1424.

[3] T.F. Chan, L.L. Lai, Yan Lie-Tong, "Performance of a three-phase AC generator with inset NdFeB permanent-magnet rotor," IEEE Trans. Energy Conversion, vol.19, no.1, pp. 88- 94, March 2004.

[4] T.F. Chan, W. Wang, L.L. Lai, "Analysis and performance of a permanent-magnet synchronous generator supplying an isolated load," IET, Electric Power Applications, vol. 4, no. 3, pp.169-176, March 2010.

[5] K. Amei, Y. Takayasu, T. Ohji and M. Sakui, “A maximum power control of wind generator system using a permanent magnet synchronous generator and a boost chopper circuit,” Proc. of the Power Conversion Conference, PCC Osaka 2002, vol. 3, 2-5 April 2002, pp. 1447 – 1452.