Novel Level Shifted PWM Technique for Unequal and Equal Power Sharing in Quasi Z Source Cascaded Multilevel Inverter for PV Systems

 ABSTRACT:

 Conventional Phase Shifted Pulse Width Modulation (PS-PWM) is a usual switching technique for Z source/Quasi Z Source (qZS) based Cascaded Multilevel Inverters (CMI) (qZS-CMI). PS-PWM scheme causes higher switching losses and creates electromagnetic interference (EMI) problem for higher number of cascaded modules. To address these issues, novel modified Level Shifted PWM (LS-PWM) technique is proposed with the aim of obtaining equal power from cascaded modules under abnormal condition. The direct use of the Alternate Phase Opposed Disposed PWM (APOD-PWM) results in an unequal power sharing between the qZSI modules, under all operating conditions. An effective carrier rotation is incorporated in the conventional APOD-PWM to make the equal power sharing between the qZSI modules. The proposed scheme is an excellent solution for the Photovoltaic (PV) systems to address the problem of partial or complete shading, temperature variation, PV module failure, and dust accumulation on the PV panels. Furthermore, the relation between the PSPWM and APOD-PWM is geometrically obtained, which indicates that the proposed modulation scheme gives higher voltage gain over LS-PWM and PS-PWM techniques. Additionally, detailed switching loss analysis for the proposed PWM methods are added to validate low switching losses and thus high efficiency. The MATLAB Simulink simulations are presented to verify the proposed modulation. Experimental prototype is developed, and the experimental outcomes validate the improved performance of the multilevel qZSI with proposed modulation.

 

KEYWORDS:

 

1.      Cascaded Multilevel Converter

2.      Impedance Source inverter (Z/qZSI)

3.      Phase Shifted Pulse Width Modulation

4.      Level Shifted Pulse Width Modulation

5.      Equal power distribution

6.       Photovoltaic (PV)

 

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:  

A novel APOD-PWM technique (equal and unequal power sharing) for the qZS-CMI has been reported in this article. This paper presents the relation between shoot through duty and modulation indices of PS-PWM and APOD-PWM. The proposed modulation technique (for qZS-CMI) combines the advantages of APOD-PWM (subsidiary of LS-PWM) and PS-PWM, resulting in high quality output voltages and harmonic free input currents drawn from the PV panels. The equal and unequal power sharing together, overcomes the drawbacks of conventional techniques. These APOD-PWM for qZS-CMI can be applied to the PV systems to address the real time problems of partial shading, dust accumulation, temperature variation and power distribution among the operating modules. To verify the advantages with proposed PWM techniques, detailed switching loss analysis, simulation and experimental results are presented. With carrier rotation in proposed PWM, equal utilization is observed whereas without carrier rotation, highest efficiency is observed. The proposed APOD-PWM techniques have nearly same THD as conventional schemes and higher voltage gain and power yielding capability with higher efficiency than PS-PWM thereby validating its feasibility for qZSI related applications.

REFERENCES:

[1] H. Abu-Rub, M. Malinowski, and K. Al-Haddad, “Power electronics for renewable energy systems,” in Transportation and Industrial Applications, Hoboken, NJ, USA: Wiley, Jul. 2014.

[2] H. Abu-Rub, J. Holtz, J. Rodriguez and G. Baoming, "Medium-Voltage Multilevel Converters—State of the Art, Challenges, and Requirements in Industrial Applications," in IEEE Trans.Ind. Electron., vol. 57, no. 8, pp. 2581-2596, Aug. 2010.

[3] J. Rodr´ıguez, J. S. Lai, and F. Z. Peng, “Multilevel inverters: A survey of topologies, controls and applications,” IEEE Trans. Ind. Electron., vol. 49, no. 4, pp. 724–738, 2002.

[4] C. D. Fuentes, C. A. Rojas, H. Renaudineau, S. Kouro, M. A. Perez and T. Meynard, "Experimental Validation of a Single DC Bus Cascaded H-Bridge Multilevel Inverter for Multistring Photovoltaic Systems," in IEEE Trans.Ind. Electron., vol. 64, no. 2, pp. 930-934, Feb. 2017.

[5] J. Rodriguez, P. Hammond, J. Pontt, R. Musalem, P. Lezana, and M. Escobar, “Operation of a medium-voltage drive under faulty conditions,” IEEE Trans. Ind. Electron., vol. 52, no. 4, pp. 1080–1085, August 2005.

 

L-C Filter Design Implementation and Comparative Study with Various PWM Techniques for DCMLI

 ABSTRACT:

 

In recent time’s multi-level inverters are widely used I industrial application, grid integration, renewable system, buildings and smart grid technology, etc. Uninterruptible power supply has become indispensable to our society. Concern with power quality and grid integration, a pure sinusoidal voltage current waveform is necessary. For such reason a design of various filters is now emerged in research area. Filters have property to smooth current and voltage waveform. This paper proposes filter design guideline for L-C filter with IGBT based multi-level inverter. An L-C circuit used at the inverter output for filtering purposes and ensuring that the THD is lower. The L-C filter cancels all harmonics and a real pure sinusoidal output voltage and current is obtained. Variable voltage and frequency supply to A.C. drives is invariably obtained from a three-phase voltage source inverter. A various pulse width modulation (PWM) schemes are used. The most widely used PWM schemes for three phase voltage source inverters are carrier-based sinusoidal PWM (SPWM) and space vector PWM (SVPWM).

In this paper a method for an asynchronous motor with inverter and L-C output filter is presented and it is verified by simulations in Matlab-Simulink. The simulation results are presented for three-phase five-level diode clamped inverter followed by three-phase L-C filter. The simulation results are compared with sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) for diode clamped multilevel inverter (DCMLI) in terms of THD.

KEYWORDS:

 

1.      DCMLI

2.      SPWM

3.      SVPWM

4.      L-C filter

5.       PWM

6.      THD

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:  

In this paper, the multicarrier SPWM and SVPWM control schemes with phase disposition (PD) is presented for DCMLI. With and without L-C filter the design algorithm of filter is presented here with THD comparison for PWM techniques. With the use of filter, the output voltage is almost sinusoidal in nature. Analysis for THD contents with use of filter on the output side of inverter shows significant improvement in the THD contents compared to the results of without using filter. This shows usefulness of L-C filter for industrial, grid integration and renewable energy applications.

REFERENCES:

[1] Hyosung Kim and Seung-ki sul “Anovel filter design for output LC filters of PWM inverters”,Journal of Power Electronics, vol. 11, no. 1, January 2011.

Thomas G. Habetler, Rajendra naik and Thomas A Nondahl “Implementation of an Inverter Output LC Filter Used for DV/DT Reduction” IEEE Transactions on Power Electronics, vol.17, no. 3, May 2002.

[3] H. W. Van Der Broeck H.C Skundenly and G.V Stanke “Analysis and realization of a pulse width modulator based on voltage space vectors” IEEE Trans. Ind. Appl., vol. 24, no. 1, pp. 142􀂱150, Jan./ Feb. 1988.

[4] Anish Gopinath, Aneesh Mohamed A. S., and M. R. Baiju “Fractal based Space Vector PWM for Multilevel Inverter- A novel approach”,IEEE Transactions on Industrial Electronics, vol. 56, no. 4, April 2009.

[5] Maryam saeedifard,Reza Iravani Josep pou “Analysis and control of  DC-Capacitor-Voltage-Drift Phenomenon of a Passive Front-End Five-level converter”, IEEE Transactions on Industrial Electronics, vol. 54, no. 6, December 2007.

Evolution of Topologies, Modeling, Control Schemes, and Applications of Modular Multilevel Converters

ABSTRACT:

 

Modular multilevel converter (MMC) is one of the most promising topologies for medium to high-voltage, high power applications. The main features of MMC are modularity, voltage and power scalability, fault tolerant and transformer-less operation, and high-quality output waveforms. Over the past few years, several research studies are conducted to address the technical challenges associated with the operation and control of the MMC. This paper presents the development of MMC circuit topologies and their mathematical models over the years. Also, the evolution and technical challenges of the classical and model predictive control methods are discussed. Finally, the MMC applications and their future trends are presented.

 

KEYWORDS:

 

1.      Capacitor voltage ripple

2.      Circulating currents

3.      High-power converters

4.      High-voltage direct current (HVDC) transmission

5.      Medium-voltage motor drive

6.      Model predictive control

7.      Modular multilevel converters

8.       Multilevel converters

9.       Power quality

10.  Pulse width modulation

11.  Submodule capacitor voltage control

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:  

The attractive features of the modular multilevel converter (MMC) played a key role in the development of new HVDC transmission systems, medium-voltage motor drives, and power quality improvement technologies. These technologies are commercialized by various leading industrial manufacturers such as GE, Alstom, ABB, Siemens, and C-EPRI. Depending on the application, the MMC has several technical issues such as circulating currents, capacitor voltage ripple, and DC-bus faults. Also, a complex control system is required to meet the several control objectives of an MMC. The past few years, numerous studies are conducted to understand the behavior of the MMC, and resulting in new topologies, mathematical models, and control schemes. This paper presents a review of the recent developments in the MMC in terms of the submodule configurations, mathematical models, pulse width modulation schemes, classical control schemes, and high-performance model predictive control methods. Also, the state-of-the-art and emerging technologies in modular multilevel converters are discussed. Finally, the list of commercial applications based on the MMC, and their technical details are provided.

REFERENCES:

[1] J. Rodriguez, L. G. Franquelo, S. Kouro, J. I. Leon, R. C. Portillo, M. . M. Prats, and M. A. Perez, “Multilevel converters: An enabling technology for high-power applications,” Proc. IEEE, vol. 97, no. 11, pp. 1786–1817, Nov 2009.

[2] S. Kouro, J. Rodriguez, B. Wu, S. Bernet, and M. Perez, “Powering the future of industry: High-power adjust/able speed drive topologies,” IEEE Ind. Appl. Mag., vol. 18, no. 4, pp. 26–39, Jul 2012.

[3] H. Abu-Rub, J. Holtz, J. Rodriguez, and G. Baoming, “Medium-voltage multilevel converters: State of the art, challenges, and requirements in industrial applications,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2581–2596, Aug 2010.

[4] P. W. Wheeler, J. Rodriguez, J. C. Clare, L. Empringham, and A. Weinstein, “Matrix converters: a technology review,” IEEE Trans. Ind. Electron., vol. 49, no. 2, pp. 276–288, Apr 2002.

[5] L. Empringham, J. W. Kolar, J. Rodriguez, P. W. Wheeler, and J. C. Clare, “Technological issues and industrial application of matrix converters: A review,” IEEE Trans. Ind. Electron., vol. 60, no. 10, pp. 4260–4271, Oct 2013.

Control of a new stand-alone wind turbine-based variable speed permanent magnet synchronous generator using quasi-Z-source inverter

 ABSTRACT:

In this paper a new variable speed permanent magnet synchronous generator (PMSG)-based stand-alone wind energy conversion system (SWECS) is proposed. The interface between the PMSG and the isolated load is accomplished by a quasi-Z-source inverter (qZSI) with battery storage system. The battery-assisted qZSI can balance the stochastic fluctuations of the wind power injected to the load and improve the voltage and frequency control. In addition to the battery storage, a dump load is used in the proposed SWECS to better maintain the active power balance and stability of the dc-link voltage during over-generation condition as well as sudden load changes. The proposed control system is able to provide an uninterrupted and reliable supply to sensitive loads under various power generation scenarios of the SWECS and sudden changes in the load demand. Moreover, the proposed controller provides maximum power point tracking (MPPT) which is essential for optimum operation of the SWECS. The validity of the proposed system is proved by simulation results carried out using MATLAB/ SIMULINK.

KEYWORDS:

1.      Permanent magnet synchronous generator (PMSG)

2.      Stand-alone wind energy conversion system (SWECS)

3.      Quasi-Z-source inverter (qZSI)

4.      Battery storage system

5.      Dump load

6.      Maximum power point tracking (MPPT)

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:  

This paper proposes a new stand-alone PMSG-based WECS using battery-assisted qZSI. The proposed battery-assisted qZSI provides the voltage boost and inversion, and energy storage in a single-stage. By introducing the dynamic model of the qZSI with battery, a closed-loop control scheme for both dc-side and ac-side of the qZSI was presented. The magnitude and frequency of the output voltage were effectively controlled through the proposed control scheme under variable wind profile and load conditions. The battery storage system located on quasi-Z-source network balances the stochastic fluctuations of the wind power injected to the load and guarantees an uninterrupted and stable power supply. On the other hand, using a dump load in the proposed system can ensure the stability of the dc-link voltage under over-generation condition of the SWECS. Lack of the dump load makes power balance difficult and can lead to voltage and frequency instability in the over-generation condition, especially when the battery reaches its maximum capacity. The dc-side controller adjusts dsh to manage the battery operation mode and maximum power extraction from the wind. Simulation results verify the performance of the proposed control scheme.

REFERENCES:

[1] C. Lumbreras, J.M. Guerrero, P. García, F. Briz, D.D. Reigosa, Control of a small wind turbine in the high wind speed region, IEEE Trans. Power Electron. 31 (10) (2016) 6980–6991.

[2] A. Kc, J. Whale, T. Urmee, Urban wind conditions and small wind turbines in the built environment: a review, Renew. Energy 131 (2019) 268–283.

[3] H. Li, Z. Chen, Overview of different wind generator systems and their comparisons, IET Renew. Power Gener. 2 (2) (2008) 123–138.

[4] Y. Wang, J. Meng, X. Zhang, L. Xu, Control of PMSG-based wind turbines for system inertial response and power oscillation damping, IEEE Trans. Sustain. Energy 6 (2) (2015) 565–574.

[5] S. Zhang, K. Tseng, D.M. Vilathgamuwa, T.D. Nguyen, X. Wang, Design of a robust grid interface system for PMSG-based wind turbine generators, IEEE Trans. Ind. Electron. 58 (1) (2011) 316–328.

Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques

 ABSTRACT:

The many different techniques for maximum power point tracking of photovoltaic (PV) arrays are discussed. The techniques are taken from the literature dating back to the earliest methods. It is shown that at least 19 distinct methods have been introduced in the literature, with many variations on implementation. This paper should serve as a convenient reference for future work in PV power generation.

 KEYWORDS

1.      Maximum power point tracking (MPPT)

2.       Photovoltaic (PV)

 SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:  

Several MPPT techniques taken from the literature are discussed and analyzed herein, with their pros and cons. It is shown that there are several other MPPT techniques than those commonly included in literature reviews. The concluding discussion and table should serve as a useful guide in choosing the right MPPT method for specific PV systems.

 REFERENCES:

[1] L. L. Buciarelli, B. L. Grossman, E. F. Lyon, and N. E. Rasmussen, “The energy balance associated with the use of a MPPT in a 100 kW peak power system,” in IEEE Photovoltaic Spec. Conf., 1980, pp. 523–527.

[2] J. D. van Wyk and J. H. R. Enslin, “A study of wind power converter with microprocessor based power control utilizing an oversynchronous electronic scherbius cascade,” in Proc. IEEE Int. Power Electron. Conf., 1983, pp. 766–777.

[3] W. J. A. Teulings, J. C. Marpinard, A. Capel, and D. O’Sullivan, “A new maximum power point tracking system,” in Proc. 24th Annu. IEEE Power Electron. Spec. Conf., 1993, pp. 833–838.

[4] Y. Kim, H. Jo, and D. Kim, “A new peak power tracker for cost-effective photovoltaic power system,” in Proc. 31st Intersociety Energy Convers. Eng. Conf., 1996, pp. 1673–1678.

[5] O. Hashimoto, T. Shimizu, and G. Kimura, “A novel high performance utility interactive photovoltaic inverter system,” in Conf. Record 2000 IEEE Ind. Applicat. Conf., 2000, pp. 2255–2260.

Single-Phase Grid-tied Transformerless Inverter of Zero Leakage Current for PV System

ABSTRACT

Multi-level transformerless inverters are widely used in grid-tied PV systems since they characterized by higher efficiency and lower cost. In this context, new topologies, modulation, and control schemes were presented to solve problems of a common-mode voltage and leakage current. This work proposes a transformerless five-level inverter with zero leakage current and ability to reduce the harmonic output content for a grid-tied single-phase PV system. The neutral of the grid links to a common on which the negative and the positive terminals of the DC-link are connected via parasitic capacitors that can eliminate the leakage current. The proposed topology, with its inherent circuit structure, leads to boost the overall efficiency. Simulation and experimental results show almost zero leakage current and a high-quality output when maintaining balanced capacitor voltages on the DC-link input. The experimental results show 1.07% THD and 96.3 % maximum efficiency when injecting a power of 1.1 kW that verify the performance of the proposed inverter with PV sources.

 

KEYWORDS:

 

1.      IGBT inverters

2.      Transformerless grid-connected photovoltaic inverter

3.      Solar PV

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

A new high-performance transformerless 5L-NPC inverter with its control strategy for a grid-tied PV system has been presented. The major advantages of the presented system can be brief as follows: 1. The topology of employing diode clamping MLI with suitable stray capacitors makes the leakage current to flow through the system in a very low value reaches zero. Furthermore, the system offers a connection between the DC-link pass bar of a solar PV array with the grid neutral terminal that results in zero leakage current. 2. The operation of the employed five-level topology results in high performance for the harmonic distortion that allows the reduction of filter components as compared with lower MLIs. 3. The proposed 5L-NPC topology eliminated the CM leakage current with 1.07% THD by using eight power switches. The results confirmed the above-stated advantages, and the proposed system offers approximately similar characteristics in reactive and real power injections. Therefore, the proposed inverter topology and its modulation scheme were a suitable and attractive solution for single-phase grid-tied PV systems. Although the proposed 5L-NPC system achieved zero CM leakage current with a very-low THD, the design is limited by eight switches that are recommended to be reduced in future work. Moreover, the presented system solved the balancing issue of the DC-link capacitors’ voltages that required for proper operation by a modulation strategy inspired in [21], we recommend easier algorithms to solve such issue.

REFERENCES:

[1] S. Padmanaban et al., “A novel modified sine-cosine optimized MPPT algorithm for grid integrated PV system under real operating conditions,” IEEE Access, vol. 7, pp. 10467–10477, 2019.

[2] N. Priyadarshi, S. Padmanaban, M. S. Bhaskar, F. Blaabjerg, and A. Sharma, “Fuzzy SVPWM-based inverter control realisation of grid integrated photovoltaicwind system with fuzzy particle swarm optimisation maximum power point tracking algorithm for a gridconnected PV/wind power generation system: Hardware implementation,” IET Electr. Power Appl., vol. 12, no. 7, pp. 962– 971, 2018.

[3] N. Priyadarshi, S. Padmanaban, P. Kiran Maroti, and A. Sharma, “An Extensive Practical Investigation of FPSO-Based MPPT for Grid Integrated PV System under Variable Operating Conditions with Anti-Islanding Protection,” IEEE Syst. J., vol. 13, no. 2, pp. 1861–1871, 2019. [4] N. Priyadarshi, S. Padmanaban, J. B. Holm-Nielsen, F. Blaabjerg, and M. S. Bhaskar, “An Experimental Estimation of Hybrid ANFIS–PSO-Based MPPT for PV Grid Integration Under Fluctuating Sun Irradiance,” IEEE Syst. J., vol. PP, pp. 1–12, 2019.

[5] N. Priyadarshi, S. Padmanaban, S. Member, M. S. Bhaskar, and F. Blaabjerg, “A Hybrid Photovoltaic-Fuel Cell-Based Single-Stage Grid Integration With Lyapunov Control Scheme,” IEEE Syst. J., vol. PP, pp. 1–9, 2019.

Modified Phase-Shifted PWM Scheme forReliability Improvement in Cascaded H-BridgeMultilevel Inverters

ABSTRACT:

 The cascaded H-bridge multilevelinverter (CHMI) is a modular structure that consists of many power semiconductor switches.With this increase in the number of power semiconductor switches, it is hard to predict and handle the failure of the devices, and hence reliability of CHMI decreases. The major cause of power semiconductor switch failure is junction temperature that is produced by power losses. The study proposes a multi-carrierpulse-width modulation (PWM) scheme for reduction in switching losses of CHMI. In the proposed modulation scheme, the two legs conduct switching operation at different frequencies for switching reduction. One leg conducts switching operation with high frequency, while the other leg conducts switching operation with fundamental frequency. The switching operations with different frequencies cause unbalanced switching loss to each leg. Therefore, the junction temperature that is based on power losses leads to different life-times for the power semiconductor switch. Additionally, the switching frequency of the two legs is alternated to evenly distribute switching losses and junction temperature. Simulation and experimental results verify the performance of the proposed PWM scheme.

KEYWORDS:                                                                   

1.      Cascaded H-bridge multilevel inverter

2.      Phase-shifted pulse-width modulationscheme

3.      Reliability of power semiconductor switch

4.      Switching loss reduction

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper proposes a modulation method for a 5-level three phase CHMI to extend the life-time and improve reliability of power semiconductor switches. The proposed method is based on the PS-PWM scheme and decreased power losses via the clamped modulation period. The existing reference voltage waveform is modified into two-type reference voltage waveforms to inject the clamped modulation period. The clamped signal reduces power loss, and other signal is reconfigured to maintain the quality of output waveforms such as the level of output voltage. Reduced power losses decrease the temperature of the power semiconductor switch, and thus the expected life-time of the powersemiconductor switch is extended by using the proposed modulation method. Additionally, the proposed modulation scheme considers the power loss balance among the switches in the same cell to improve the reliability of the CHMI. The rotation method with 1/4 period is applied to proposed scheme for even switching loss and temperature among switches. Therefore, the all switches in proposed method are decreased temperature and increased life-time evenly. The performance of the proposed method is verified via simulation and experimental results.

REFERENCES:

[1] B.Wu, High-Power Converter and AC Drives. Hoboken, NJ, USA:Wiley,2006.

[2] D. Karwatzki and A. Mertens, ``Generalized control approach for a class of modular multilevel converter topologies,'' IEEE Trans. Power Electron., vol. 33, no. 4, pp. 2888_2900, Apr. 2018.

[3] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. G. Franquelo, B.Wu, J. Rodriguez, M. A. Pérez, 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] J. Rodriguez, S. Bernet, B. Wu, J. O. Pontt, and S. Kouro, ``Multilevel Voltage-Source-Converter topologies for industrial medium-voltage drives,'' IEEE Trans. Ind. Electron., vol. 54, no. 6, pp. 2930_2945, Dec. 2007.

[5] G. P. Adam, I. A. Abdelsalam, K. H. Ahmed, and B.W.Williams, ``Hybrid multilevel converter with cascaded H-bridge cells for HVDC applications: Operating principle and scalability,'' IEEE Trans. Power Electron., vol. 30, no. 1, pp. 65_77, Jan. 2015.