Analysis of a Modified Single Phase Multilevel Cascaded Inverter Circuit

ABSTRACT:

 

A modified circuit of single phase five level cascaded inverter state of art design topology is discussed. The modified circuit has reduced number of switches and a comparison of the total harmonic distortion with various pulse width modulation techniques was carried out. A multicarrier sinusoidal pulse width modulation approach is used to control the distortion in the inverter. Several types of multi carrier pulse width modulation techniques have been analyzed in this paper. For higher modulation index value the Phase Disposition offers the lowest level of Total harmonic distortion. To validate the objective MATLAB/Simulink simulation software was used and it has been justified by using the experimental results.

KEYWORDS:

 

1.      Sinusoidal pulse width modulation(SPWM)

2.      Cascaded multi level inverter (CMLI)

3.      Total harmonic distortion (THD)

 

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

By using state of art design the proposed converter circuit was designed and the experimental verification of simulation results was carried out. To remove the harmonics, SPWM was used and the overall performance of the system was improved. Results obtained show the successful harmonics elimination. By utilizing the different configuration of multilevel SPWM techniques the harmonics are reduced significantly. For higher modulation index value the Phase Disposition offers the lowest level of Total harmonic distortion.

REFERENCES:

[1] C. Govindaraju1 and K. Baskaran, “Performance Improvement of Multiphase Multilevel Inverter Using Hybrid Carrier Based Space Vector Modulation”, International Journal on Electrical Engineering and Informatics, vol. 2, pp. 137- 149, 2014.

[2] C.Govindaraju and Dr.K.Baskaran, “Optimized Hybrid Phase Disposition PWM Control Method for Multilevel Inverter”, International Journal of Recent Trends in Engineering, vol. 1, no. 3, pp129-134, May 2014.

[3] Zhong Du1, Leon M. Tolbert2,3, John N. Chiasson2, and Burak Özpineci3, “A Cascade Multilevel Inverter Using a Single DC Source”, Applied Power Electronics Conference and Exposition, APEC '06. Twenty-First Annual IEEE, pp. 426-430, 2006.

[4] P. Thongprasri,“A 5-Level Three-Phase Cascaded Hybrid Multilevel Inverter”, International Journal of Computer and Electrical Engineering, Vol. 3, No. 6, December 2011, pp 789-794.

[5] C.Kiruthika1,T.Ambika,Dr.R.Seyezhai, “simulation of cascaded multilevel inverter using hybrid pwm technique”, International Journal of Systems, Algorithms & Applications Volume 1, Issue 1, December 2011, pp-18-21.

 

A Voltage and Frequency Droop Control Method forParallel Inverters

 ABSTRACT: 

In this paper, a new control method for the parallel operation of inverters operating in an island grid or connected to an infinite bus is described. Frequency and voltage control, including mitigation of voltage harmonics, are achieved without the need for any common control circuitry or communication between inverters. Each inverter supplies a current that is the result of the voltage difference between a reference ac voltage source and the grid voltage across a virtual complex impedance. The reference ac voltage source is synchronized with the grid, with a phase shift, depending on the difference between rated and actual grid frequency. A detailed analysis shows that this approach has a superior behavior compared to existing methods, regarding the mitigation of voltage harmonics, short-circuit behavior and the effectiveness of the frequency and voltage control, as it takes the to line impedance ratio into account. Experiments show the behavior of the method for an inverter feeding a highly nonlinear load and during the connection of two parallel inverters in operation.

KEYWORDS:

 

1.      Autonomous power systems

2.      Converter control

3.      Dispersed generation

4.      Finite output-impedance ac voltage source emulation

5.      Frequency and voltage droops

6.      Harmonics

7.       Parallel connection

8.      Power quality

9.      Microgrids

10.  Stand-alone systems

11.  Uninterruptible power supplies (UPS)

12.  Virtual impedance

13.  Voltage source inverter

14.   Mixed voltage-current control

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

A time-domain method for controlling voltage and frequency using parallel inverters connected to the mains or in an island grid is developed. By imitating a voltage source with a complex finite-output impedance, voltage droop control is obtained. Frequency droop control results from synchronizing the power source with the grid, with a phase angle difference that depends on the difference between rated and actual grid frequency. Compared to existing techniques, the described method exhibits superior behavior, considering the mitigation of voltage harmonics, the behavior during short-circuit and, in the case of a non-negligible line resistance, the “efficient” control of frequency and voltage. Two experiments are included to show the described behavior.

REFERENCES:

[1] A. Tuladhar, H. Jin, T. Unger, and K. Mauch, “Parallel operation of single phase inverter modules with no control interconnections,” in Proc. IEEE-APEC’97 Conf., Feb. 23–27, 1997, vol. 1, pp. 94–100.

[2] E. A. A. Coelho, P. C. Cortizo, and P. F. D. Garcia, “Small-signal stability for parallel-connected inverters in stand-alone AC supply systems,” IEEE Trans. Ind. Appl., vol. 38, no. 2, pp. 533–542, Mar./Apr. 2002.

[3] M. C. Chandorkar, D. M. Divan, and R. Adapa, “Control of parallel connected inverters in standalone AC supply systems,” IEEE Trans. Ind. Appl., vol. 29, no. 1, pp. 136–143, Jan./Feb. 1993.

[4] A. Engler, “Regelung von Batteriestromrichtern in modularen und erweiterbaren Inselnetzen,” Ph.D. dissertation, Dept. Elect. Eng., Univ. Gesamthochschule Kassel, Kassel, Germany, 2001.

[5] M. Hauck and H. Späth, “Control of three phase inverter feeding an unbalanced load and operating in parallel with other power sources,” in Proc. EPE-PEMC’02 Conf., Sep. 9–11, 2002.

Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

ABSTRACT:

DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

 

KEYWORDS:

1.      Coupled inductors

2.      Multilevel converter

3.      Multistage converter

4.      Pulse width modulated (PWM) boost converter

5.      Switched capacitor (SC)

6.      Switched inductor

7.      Switched mode step-up dc–dc converter

8.      Transformer

9.      Voltage lift (VL)

10.  Voltage multiplier

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

The ongoing technological progress in high-voltage step-up dc–dc converter has five primary drivers—energy efficiency, power density, cost, complexity, and reliability—all of which also influence each other to some extent. Table X, along with the spider wave diagram in Fig. 34, provides a comparative summary of various voltage-boosting techniques in terms of their major characteristics (i.e., power level, cost, reliability, efficiency, power density, weight, integration, and complexity).This view facilitates quick selection between related alternatives for special load and application requirements. Each voltage boosting technique has its own unique features and suitable applications, and there is no one-size-fits-all solution. Nevertheless, it is generally not fair to permanently favor any particular technique or solution. The converter topology and control method, which was seen as complex and inefficient a decade back, has now become a key solution for many industries and applications. In this manner, new topologies based on different and often merged voltage-boosting techniques will continue to appear in order to meet and improve the performance of different applications. Thanks to the progress in power-semiconductor devices, new widebandgap devices (GaN, SiC, etc.), advanced magnetic materials, high-performance digital control platforms, and advanced design and packaging including thermal management (3-D integrated) have all become a reality. These advances will undeniably enablemore powerful and advanced power converter solutions for the next generation of power conversion systems. Overall, the authors hope that this comprehensive survey will be a useful resource to help both academic and industry readers comprehend step-up dc–dc converter topologies and identify their respective pros and cons.

REFERENCES:

[1] T. G. Wilson, “The evolution of power electronics,” IEEE Trans. Power Electron., vol. 15, no. 3, pp. 439–446, May 2000.

[2] B. K. Bose, “The past, present, and future of power electronics,” IEEE Ind. Electron. Mag., vol. 3, no. 2, pp. 7–11, Jun. 2009.

[3] M. H. Rashid, Power Electronics Handbook: Devices Circuitsand Application, 3rd ed. Burlington, MA, USA: Elsevier, 2011.

[4] M.K.Kazimierczuk, Pulse-WidthModulated DC-DC Power Converters. Chichester, U.K.: Wiley, 2008.

[5] R.W. Erickson and D. Maksimovic, Fundamentals of Power Electronics, 2nd ed. Norwell, MA, USA: Kluwer, 2001.

Single-Phase Shunt Active Filter Interfacing Renewable Energy Sources with the Power Grid

ABSTRACT:

This paper presents a single-phase Shunt Active Filter combined with a Maximum Power Point Tracker (MPPT) connected to a solar panel array. The Shunt Active Filter’s power stage consists of a two-leg IGBT inverter commanded by a Digital Signal Processor (DSP) with control based on the Theory of Instantaneous Reactive Power (p-q Theory). The MPPT is based on a step-up circuit commanded by a DSP with MPPT Algorithm implemented. The output of the MPPT circuit is connected to the DC side of the Shunt Active Filter. The system is capable of compensating power factor and current harmonics, and at the same time, using the same inverter, injecting in the power grid electric energy produced by solar panels, regulated by the MPPT. There will be presented results of the system operating in an electrical installation under different conditions, as well as the hardware configuration and specifications.

 

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper presented experimental results of a single-phase Shunt Active Filter combined with a MPPT, injecting energy in the electric grid produced by a solar panel array. The results show the performance of the Shunt Active Filter operating alone, and also the complete system behavior in compensation and energy injection tasks simultaneously. The presented configuration shows some advantages over the traditional ones since it gathers functionalities of different equipments using the same hardware to accomplish the different tasks. The only drawback of the presented configuration is that the power inverter has to be increased because the injected current is composed by two components: a component that represents the renewable energy to inject in the electric grid and a component to compensate harmonics and power factor of the facility.The presented Active Power Filters are currently in industrialization process by the company EFACEC SGPS S.A.

REFERENCES:

 [1] L. Gyugi and E. C. Strycula, “Active AC Power Filters”, IEEE-IAS Annual Meeting Record, 1976, pp. 529-535.

[2] J. G. Pinto, R. Pregitzer, Luís F. C. Monteiro, João L. Afonso, “3 Phase 4 Wire Shunt Active Power Filter with Renewable Energy Interface”, Proceedings of ICREPQ’07- International Conference on Renewable Energies and Power Quality, 28-30 March 2007, Seville, Spain, ISBN:978-84-611-4707-6.

[3] H. Akagi, Y. Kanazawa, A. Nabae, “Generalized Theory of the Instantaneous Reactive Power in Three-Phase Circuits”, IPEC'83 - Int. Power Electronics Conf., Tokyo, Japan, 1983, pp. 1375-1386.

[4] H. Akagi, Y. Kanazawa, A. Nabae, “Instantaneous Reactive Power Compensator Comprising Switching Devices without Energy Storage Components”, IEEE Trans. Industry Applic., vol. 20, May/June 1984.

[5] E. H. Watanabe, R. M. Stephan, M. Aredes, “New Concepts of Instantaneous Active and Reactive Powers in Electrical Systems with Generic Loads”, IEEE Trans. Power Delivery, vol. 8, no. 2, April 1993,pp. 697-703.

Control of a Stand Alone Variable Speed Wind Turbine with a Permanent Magnet Synchronous Generator

 ABSTRACT:

A novel control strategy for the operation of a permanent magnet synchronous generator (PMSG) based stand alone variable speed wind turbine is presented in this paper,. The direct drive PMSG is connected to the load through a switch mode rectifier and a vector controlled pulse width modulated (PWM) IGBT-inverter. The generator side switch mode rectifier is controlled to achieve maximum power from the wind. The load side PWM inverter is using a relatively complex vector control scheme to control the amplitude and frequency of the inverter output voltage. As there is no grid in a stand-alone system, the output voltage has to be controlled in terms of amplitude and frequency. The stand alone control is featured with output voltage and frequency controller capable of handling variable load. A damp resistor controller is used to dissipate excess power during fault or over-generation. The potential excess of power will be dissipated in the damp resistor with the chopper control and the dc link voltage will be maintained. Extensive simulations have been performed using Matlab/Simpower. Simulation results show that the controllers can extract maximum power and regulate the voltage and frequency under varying load condition. The controller performs very well during dynamic and steady state condition.

 

KEYWORDS:

 

1.      Permanent magnet synchronous generator

2.      Maximum power extraction

3.      Switch-mode rectifier

4.      Stand alone variable speed wind turbine

5.      Voltage and frequency control

 

SOFTWARE: MATLAB/SIMULINK

 

CONCLUSION:

Control strategy for a stand alone variable speed wind turbine with a PMSG is presented in this paper. A simple control strategy for the generator side converter to extract maximum power is discussed and implemented using Simpower dynamic system simulation software. The controller is capable to maximize output of the variable speed wind turbine under fluctuating wind. The load side PWM inverter is controlled using vector control scheme to maintain the amplitude and frequency of the inverter out put voltage. It is seen that the controller can maintain the load voltage and frequency quite well at constant load and under varying load condition. The generating system with the proposed control strategy is suitable for a small scale standalone variable speed wind turbine installation for remote area power supply. The simulation results demonstrate that the controller works very well and shows very good dynamic and steady state performance

 

 

REFERENCES:

[1] Müller, S., Deicke, M., and De Doncker, Rik W.: ‘Doubly fed induction genertaor system for wind turbines’, IEEE Industry Applications Magazine, May/June, 2002, pp. 26-33.

[2] H. Polinder, F. F. A. van der Pijl, G. J. de Vilder, P. J. Tavner, "Comparison of direct-drive and geared generator concepts for wind turbines," IEEE Trans. On energy conversion, vol . 21, no. 3, pp. 725-733, Sept. 2006.

[3] T. F. Chan, L. L. Lai, "Permanenet-magnet machines for distributed generation: a review," in proc. 2007 IEEE power engineering annual meeting, pp. 1-6.

[4] M. De Broe, S. Drouilhet, and V. Gevorgian, “A peak power tracker for small wind turbines in battery charging applications,” IEEE Trans. Energy Convers., vol. 14, no. 4, pp. 1630–1635, Dec. 1999.

[5] R. Datta and V. T. Ranganathan, “A method of tracking the peak power points for a variable speed wind energy conversion system,” IEEE Trans. Energy Convers., vol. 18, no 1, pp. 163–168, Mar. 1999.

Control of Permanent-Magnet Generators Applied to Variable-Speed Wind-Energy Systems Connected to the Grid

 ABSTRACT:

Wind energy is a prominent area of application of variable-speed generators operating on the constant grid frequency. This paper describes the operation and control of one of these variable-speed wind generators: the direct driven permanent magnet synchronous generator (PMSG). This generator is connected to the power network by means of a fully controlled frequency converter, which consists of a pulse width-modulation (PWM) rectifier, an intermediate dc circuit, and a PWM inverter. The generator is controlled to obtain maximum power from the incident wind with maximum efficiency under different load conditions. Vector control of the grid-side inverter allows power factor regulation of the windmill. This paper shows the dynamic performance of the complete system. Different experimental tests in a 3-kW prototype have been carried out to verify the benefits of the proposed system.

KEYWORDS: 

1.      Permanent-magnet generators

2.      Pulse width modulated (PWM) power converters

3.      Wind energy

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This work shows the performance of a direct-driven permanent-magnet synchronous generator used in variable speed wind-energy systems. When exciting the system with a real wind profile, the system is able to track maximum power using generated power as input. The speed controller sets the generator torque command, which is achieved through a current control loop. An efficient generator control has been proposed. To achieve this objective, the optimum generator d-axis current component is imposed by the power converter, i.e., the current that leads to the minimum losses. The proposed system has been implemented in a real-time application, with a commercial permanent-magnet synchronous generator and a dc drive that emulates the wind turbine behaviour. The real-time process is running in a dSPACE board that includes a TMS320C31 floating-point DSP. Experimental results show the appropriate behavior of the system.

REFERENCES:

[1] A. Grauers, “Efficiency of three wind energy generator systems” IEEE Trans. Energy Convers, vol. 11, no. 3, pp. 650–657, Sep. 1996.

[2] E. Spooner and A. C. Williamson, “Direct coupled, permanent magnet generators for wind turbine applications,” Proc. Inst. Elect. Eng.—Elect. Power Appl., vol. 143, no. 1, pp. 1–8, 1996.

[3] R. Pe˜na, J. C. Clare, and G. M. Asher, “Doubly fed induction generator using back-to-back PWM converters and its application to variable-speed wind-energy generation,” Proc. Inst. Elect. Eng.—Elect. Power Appl., vol. 143, no. 3, pp. 231–241, May 1996.

[4] Z. Chen and E. Spooner, “Simulation of a direct drive variable speed energy converter,” in Proc. Int. Conf. Electrical Machines, Istanbul, Turkey, 1998, pp. 2045–2050.

[5] A. Grauers “Design of direct driven permanent magnet generators for wind turbines,” M.S. thesis, Chalmers Univ. Technol., G¨oteborg, Sweden, 1996.

Operation, Control, and Applications of the Modular Multilevel Converter: A Review

ABSTRACT:

 The modular multilevel converter (MMC) has been a subject of increasing importance for medium/high power energy conversion systems. Over the past few years, significant research has been done to address the technical challenges associated with the operation and control of the MMC. In this paper, a general overview of the basics of operation of the MMC along with its control challenges are discussed, and a review of state of-the-art control strategies and trends is presented. Finally, the applications of the MMC and their challenges are highlighted.

KEYWORDS:

1.      Capacitor Voltage Balancing

2.      Circulating Current Control

3.      High-Voltage Direct Current (HVDC) Transmission

4.      Modular Multilevel Converter (MMC)

5.      Modulation Techniques

6.      Redundancy

7.      Variable-Speed Drive Systems

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:  

The salient features of the MMC, i.e., its modularity and scalability enable it to conceptually meet any voltage level requirements with superior harmonic performance, reduced rating values of the converter components and improved efficiency. Over the past few years, the MMC has become a subject of interest for various medium to high voltage/power system and industrial applications including HVDC transmission systems, FACTS, medium-voltage variable-speed drives, and medium/high voltage dc-dc converters.

For power system applications, e.g., HVDC systems and FACTS, the MMC has reached a certain level of maturity and seems to stand as the most promising technology as a number of MMC-HVDC systems and STATCOMs has been successfully implemented and installed. For medium-voltage variable-speed drives, there is still a plenty of room for further development and to address the operational and control issues of the MMC, specifically under constant-torque low-speed operation. One major problem that needs to be addressed is to minimize the magnitude of the capacitor voltage ripple of the converter SMs at low frequencies without sacrificing the converter efficiency, thereby making a reasonable tradeoff between the converter size/volume/cost and efficiency.

The introduction of a family of modular multilevel dc-dc converters, originated from the MMC topology, has opened up a new avenue on research and development of medium/high voltage dc-dc converters. To take the full advantage of these converters for various applications, advanced modulation strategies that enable high voltage conversion ratio, high efficiency and reduced component stresses are required. With a significant amount of MMC-derived converter topologies and applications, it is concluded that development of novel modulation and control strategies will be a major driving factor to shape the future of MMC applications.

REFERENCES:

[1] G. Ding, G. Tang, Z. He, and M. Ding, “New technologies of voltage source converter (VSC) for HVDC transmission system based on VSC,” in Proc. IEEE Power and Energy Society General Meeting, 2008, pp. 1–8.

[2] S. Allebrod, R. Hamerski, and R. Marquardt, “New Transformerless, Scalable Modular Multilevel Converters for HVDC-Transmission,” in Proc. IEEE Power Electronics Specialists Conf. (PESC), 2008, pp. 174– 179.

[3] J. Dorn, H. Huang, and D. Retzmann, “A New Multilevel Voltage- Sourced Converter Topology for HVDC Applications,” in Proc. Cigre Session, B4-304, Paris, 2008.

[4] R. Marquardt, “Modular multilevel converter: An universal concept for HVDC-networks and extended DC-bus-applications,” in Proc. International Power Electronics Conf., Jun. 2010, pp. 502–507.

[5] J. Dorn, H. Huang, and D. Retzmann, “Novel Voltage-Sourced Converters for HVDC and FACTS Applications,” in Proc. Conf. Cigre Symposium Osaka, Japan, 2007.