Low Switching Frequency Based Asymmetrical Multilevel Inverter Topology With Reduced Switch Count

 ABSTRACT:

 The inceptions of multilevel inverters (MLI) have caught the attention of researchers for medium and high power applications. However, there has always been a need for a topology with a lower number of device count for higher efficiency and reliability. A new single-phase MLI topology has been proposed in this paper to reduce the number of switches in the circuit and obtain higher voltage level at the output. The basic unit of the proposed topology produces 13 levels at the output with three dc voltage sources and eight switches. Three extentions of the basic unit have been proposed in this paper. A detailed analysis of the proposed topology has been carried out to show the superiority of the proposed converter with respect to the other existing MLI topologies. Power loss analysis has been done using PLECS software, resulting in a maximum ef_ciency of 98.5%. Nearest level control (NLC) pulse-width modulation technique has been used to produce gate pulses for the switches to achieve better output voltage waveform. The various simulation results have been performed in the PLECS software and a laboratory setup has been used to show the feasibility of the proposed MLI topology.

KEYWORDS:

1.      DC - AC converter

2.      Multilevel inverter

3.      Reduce switch count

4.       Nearest level control (NLC)

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:   

The paper presents a novel MLI topology with multiple exten- sion capabilities. The basic unit of the proposed topology produces 13 levels using eight unidirectional switches and three dc voltage sources. Three different extension of the basic unit has been proposed. The performance analysis of the basic unit of the proposed topology has been done and the comparative results with some recently proposed topologies in literature have been presented in the paper. Further, a power loss analysis of the dynamic losses (switching and conduction) in the MLI has also been presented, which gives the maximum efficicnecy of the basic unit as 98.5%. The power loss distribution in all the switches for different combination of loads have also been demonstrated in the paper. The performance of the proposed topology has been simulated with dynamic modulation indexes and different combination of loads using PLECS software. A prototype of the basic unit has been developed in the laboratory and the simulation results have been validated using the different expriemntal results considering different modulation indexes.

REFERENCES:

[1] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. G. Franquelo, B.Wu, J. Rodriguez, M. A. Perez, and J. I. Leon, ``Recent advances and industrial applications of multilevel converters,'' IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553_2580, Aug. 2010.

[2] H. Aburub, J. Holtz, and J. Rodriguez, ``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, Dec. 2010.

[3] H. Akagi, ``Multilevel converters: Fundamental circuits and systems,'' Proc. IEEE, vol. 105, no. 11, pp. 2048_2065, Nov. 2017.

[4] J. I. Leon, S. Vazquez, and L. G. Franquelo, ``Multilevel converters: Control and modulation techniques for their operation and industrial appli- cations,'' Proc. IEEE, vol. 105, no. 11, pp. 2066_2081, Nov. 2017.

[5] J. Venkataramanaiah, Y. Suresh, and A. K. Panda, ``A review on symmet- ric, asymmetric, hybrid and single DC sources based multilevel inverter topologies,'' Renew. Sustain. Energy Rev., vol. 76, pp. 788_812, Sep. 2017.

Fast Sensor-Less Voltage Balancing and Capacitor Size Reduction in PUC5 Converter Using Novel Modulation Method

ABSTRACT:

 This paper proposes a novel sensor-less switching method based on logic gates for five-level packed U-cell (PUC5) converter. It comprises only two level-shifted triangular carriers and logic gates. Hence, the number of triangular carriers is halved and the switching states table is eliminated, which cause remarkable reduction in complexity of the proposed modulation method. Moreover, employing the proposed sensor-less switching method leads to decrease in the PUC5 capacitor value by factor of carrier ratio, fast self-balancing of the PUC5 capacitor voltage, and halving the output LC filter inductor and capacitor values in stand-alone mode as well as the grid link inductor value in grid connected mode. In addition, the PUC5 converter start-up transient time is considerably decreased and the first switching harmonic cluster frequency is doubled, which lead to notable improvement of steady-state and dynamic performance of the PUC5 converter. The proposed sensor-less switching method has been implemented in both stand-alone and grid-connected operating modes of PUC5 converter. Provided simulation and experimental results verify the feasibility and effectiveness of the proposed sensor-less switching method as well as its improved dynamic and steady state performances in both stand-alone and grid-connected modes.

KEYWORDS:

 

1.      Capacitor size reduction

2.      Logic gate based modulation method

3.      Multilevel inverter

4.      Packed U-cell (PUC)

5.      Sensor-less control

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:  

In this paper, a novel sensor-less switching method based on logic gates was proposed for PUC5 converter. It comprises only two level shifted triangular carriers and logic form equations and does not have switching states table. Hence, the proposed method does not compel complex calculations and can be easily implemented on low-cost microcontrollers. By utilizing the proposed sensor-less modulation method, the charging and discharging of capacitor is balanced in each switching period, which causes fast self-balancing of the PUC5 capacitor voltage. Moreover, employing the proposed sensor-less switching method leads to decrease the PUC5 capacitor value by factor of carrier ratio ( 0 SW C F R F = ), and halving the output LC filter inductor and capacitor sizes in stand-alone mode as well as the grid link inductor size in gridconnected mode. In addition, the PUC5 converter start-up transient time is considerably decreased and the first switching harmonic cluster frequency is doubled, which lead to notable improvement of steady-state and dynamic performance of PUC5 converter. The proposed sensor-less switching method has been evaluated for both stand-alone and grid-connected modes. An external current controller has been used to control the injected active and reactive power to the grid. Provided simulation and experimental results for stand-alone and gridconnected gridconnected modes verify the feasibility and effectiveness of the proposed sensor-less switching method as well as its improved dynamic and steady state performance.

REFERENCES:

[1] J. Li, S. Bhattacharya, and A. Q. Huang, "A New Nine-Level Active NPC (ANPC) Converter for Grid Connection of Large Wind Turbines for Distributed Generation," IEEE Trans. Power Electron., vol. 26, pp. 961-972, 2011.

[2] M. Abarzadeh, H. M. Kojabadi, and L. Chang, "A Modified Static Ground Power Unit Based on Novel Modular Active Neutral Point Clamped Converter," IEEE Trans. Ind. Appl., vol. 52, pp. 4243-4256, 2016.

[3] M. Abarzadeh, H. M. Kojabadi, F. Deng, and Z. Chen, "Enhanced static ground power unit based on flying capacitor based h-bridge hybrid active-neutral-point-clamped converter," IET Power Electron., vol. 9, pp. 2337-2349, 2016.

[4] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. G. Franquelo, B. Wu, et al., "Recent Advances and Industrial Applications of Multilevel Converters," IEEE Trans. Ind. Electron., vol. 57, pp. 2553-2580, 2010.

[5] 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, pp. 2930-2945, 2007.

Evaluation of Level-Shifted and Phase-Shifted PWM Schemes for Seven Level Single-Phase Packed U Cell Inverter

 ABSTRACT:

 An evaluation of level shifted and phase shifted triangular and sawtooth carrier modulation schemes for a seven level packed U cell (PUC) inverter is presented in this paper. The investigated PUC is the recently introduced topology for multilevel inverter having reduced switch count in comparison to the conventional topologies of multilevel inverters. The PUC inverter has six switches for 7 level inverter which is very less in comparison to the conventional topologies. In this paper, the level-shifted pulse width modulation (LS-PWM) and phase-shifted PWM (PS-PWM) for triangular and sawtooth carrier are presented and compared. A comparative harmonic analysis for all the cases is performed and results are presented in the paper. The difference in harmonics of the two modulation methods given by the theoretical approach for both the carrier is validated by the experimental results. DC voltage controller and load current controller of the PUC inverter are also designed and presented. The investigated PUC topology is tested in dynamic and steady state conditions and results obtained are presented. The analysis is done and validated using simulation in MATLAB® Simulink environment and experimental approaches using FPGA platform.

KEYWORDS:

1.      Level shift

2.       Multilevel inverter

3.       Modulation

4.      Phase shift

5.       PI controller

6.      PUC inverter

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:  

The paper has presented the comparison of different PWM schemes which can be applied to the PUC inverter. Investigating the suitable modulation schemes is very essential with respect to local grid integration, as the power quality is directly dependent on THD. Triangular carrier based PWM schemes is exhibiting the better result than the sawtooth carrier based PWM schemes as the triangular level shifted carrier PWM scheme is better as compared to sawtooth level shifted carrier because in triangular level shifted carrier both edges (falling and rising) of pulses are modulated which improves the harmonic spectrum. However, in the sawtooth level shifted carrier only rising edges are modulated. Hence triangular level shifted carrier PWM scheme can be applied for integrating the PUC inverter with PV and local grid systems. Triangular level shifted carrier PWM scheme for PUC inverter has been suggested based on observing the THD in voltage and current which are respectively just 17.92% and 2.43%. The whole system i.e. solar panel, boost converter with PUC inverter will be very cost effective, besides having good  reliability and power quality as it has the minimum number of power electronics devices compared to previously introduced multilevel inverter topologies. With reduced number of capacitors and power switches seven levels of voltages have been achieved for PUC inverter.

REFERENCES:

[1] F. A. Rahman, M. M. A. Aziz, R. Saidur, W. A. A. Bakar, M. R. Hainin, R. Putrajaya, and N. A. Hassan, “Pollution to solution: Capture and sequestration of carbon dioxide (CO2) and its utilization as a renewable energy source for a sustainable future”, Renewable and Sustainable Energy Reviews,vol. 71, pp. 112-126, May 2017.

[2] Y. Yang, A. Sangwongwanich, and F. Blaabjerg, “Design for reliability of power electronics for grid-connected photovoltaic systems,” in CPSS Transactions on Power Electronics and Applications, vol. 1, no. 1, pp. 92-103, Dec. 2016..

[3] J. Rodriguez, J.-S. Lai, and F. Z. Peng, “Multilevel inverters: a survey of topologies, controls, and applications,” Industrial Electronics, IEEE Transactions on, vol. 49, pp. 724-738, 2002.

[4] Q. M. Attique, Y. Li, and K. Wang, “A survey on space-vector pulse width modulation for multilevel inverters,” in CPSS Transactions on Power Electronics and Applications, vol. 2, no. 3, pp. 226-236, Sept. 2017.

[5] Z. Mohzani, B. P. McGrath, and D. G. Holmes, “A generalized natural balance model and balance booster filter design for three-level Neutral- Point-Clamped converters,” in IEEE Transactions on Industry Applications, vol. 51, no. 6, pp. 4605-4613, Nov.-Dec. 2015.

Design of a Proportional Resonant Controller for Packed U Cell 5 Level Inverter for Grid-Connected Applications

 ABSTRACT:

 In this paper, the design of a proportional resonant (PR) controller for the packed U cell (PUC) 5 level inverter is presented. The objective of the presented work is to present a better solution for current control in grid connected application of the investigated topology. A suitable LCL filter is designed along with the PR control scheme for grid connection. Simulation is performed in MATLAB®/Simulink simulation environment and the theoretical as well as simulation results are validated through experimental results. The simulation results shown in the paper includes both the steady state and the dynamic conditions. The key equations, block diagram, simulation results and experimental results are shown and discussed in the paper.

 KEYWORDS:

1.      Packed U Cell

2.       Proportional Resonant Controller

3.      Multi Level Inverter

4.      Grid Connected

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:  

The paper has discussed the design of a proportional resonant controller for packed U cell 5 level inverter for grid-connected applications. First the theoretical analysis has been done in the paper and the same is verified by the simulation results which is further validated by the experimental results. It can be observed that the THD is very minimal and follows the IEEE standards. The single phase 5 level PUC inverter can be extended to 3 phase and 5 phase PUC inverter in the future for connection to the 3 phase grid and 5 phase motor drives application. The control algorithm can be developed in future for integration with the 3 phase grid and 5 phase motor drives application as discussed above.

REFERENCES:

[I] L. Hadjidemetriou, E. Kyriakides and F. Blaabjerg, "A Robust Synchronization to Enhance the Power Quality of Renewable Energy Systems," in IEEE Transactions on Industrial Electronics, vol. 62, no. 8, pp. 4858-4868, Aug. 2015 ..

[2] F. Blaabjerg, Zhe Chen and S. B. Kjaer, "Power electronics as efficient interface in dispersed power generation systems," in IEEE Transactions on Power Electronics, vol. 19, no. 5, pp. 1184-1194, Sept. 2004.

[3] 1. Rodriguez, J ih-Sheng Lai and Fang Zheng Peng, "Multilevel inverters: a survey of topologies, controls, and applications," in IEEE Transactions on Industrial Electronics, vol. 49, no. 4, pp. 724-738, Aug 2002.

[4] A. Tariq, M. A Husain, M. Ahmad and M. Tariq, "Simulation and study of a grid connected multilevel converter (MLC) with varying DC input," Environment and Electrical Engineering (EEEiC), 2011 10^th international Conference on, Rome, 2011 , pp. 1-4.

[5] K. K. Gupta, A Ranjan, P. Bhatnagar, L. K. Sahu and S. Jain, "Multilevel Inverter Topologies With Reduced Device Count: A Review," in Feee Transactions on Power Electronics, vol. 31, no. I, pp. 135-151 , Jan. 2016.

Artificial Neural Network for Control and GridIntegration of Residential Solar Photovoltaic Systems

ABSTRACT:

 Residential solar photovoltaic (PV) energy is becoming an increasingly important part of the world's renewable energy. A residential solar PV array is usually connected to the distribution grid through a single-phase inverter. Control of the single-phase PV system should maximize the power output from the PV array while ensuring overall system performance, safety, reliability, and controllability for interface with the electricity grid. This paper has two main objectives. The first objective is to develop an artificial neural network (ANN) vector control strategy for a LCL-filter based single-phase solar inverter. The ANN controller is trained to implement optimal control, based on approximate dynamic programming. The second objective is to evaluate the performance of the ANN-based solar PV system by (a) simulating the PV system behavior for grid integration and maximum power extraction from solar PV array in a realistic residential PV application and (b) building an experimental solar PV system for hardware validation. The results demonstrate that a residential PV system using the ANN control outperforms the PV system using the conventional standard vector control method and proportional resonant control method in both simulation and hardware implementation. This is also true in the presence of noise, disturbance, distortion, and non-ideal conditions.

KEYWORDS:

 

1.      Artificial neural networks

2.      DC-AC power converters

3.       DC-DC power converters

4.      Dynamic programming

5.      Maximum power point tracker

6.      Optimal control

7.      Solar power generation

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper proposes a single-phase, residential solar PV system based on artificial neural networks and adaptive dynamic programming for MPPT control and grid integration of a solar photovoltaic array through an LCL-filter based inverter. The proposed artificial neural network controller implements the optimal control based on the approximate dynamic programming. Both the simulation and hardware experiment results demonstrate that the solar PV system using the ADP-based artificial neural network controller has more improved performance than that using the proportional resonant or conventional standard vector control techniques, such as no requirement for damping resistance, more reliable and efficient extraction of solar power, more stable DC-link voltage, and more reliable integration with the utility grid. Using the ADP-based neural network control technique, the harmonics are significantly reduced and the system shows much stronger adaptive ability under uncertain conditions, which would greatly benefit the integration of small-scale residential solar photovoltaic systems into the grid.

REFERENCES:

[1] Renewable Energy World Editors. (2014, Nov. 12). Residential Solar Energy Storage Market Could Approach 1 GW by 2018. Available: http://www.renewableenergyworld.com.

[2] R. A. Mastromauro, M. Liserre and A. D. Aquila, “Control Issues in Single-Stage Photovoltaic Systems: MPPT, Current and Voltage Control”, IEEE Trans. Ind. Informatics, vol. 8, no. 2, pp. 241-254, May 2012.

[3] E. Lorenzo, G. Araujo, A. Cuevas, M. Egido, J. Miñano and R. Zilles, Solar Electricity: Engineering of Photovoltaic Systems, Progensa, Sevilla, Spain, 1994.

[4] J. M. Carrasco, L. G. Franquelo, J. T. Bialasiewicz, E. Galván, R. C. P. Guisado, M. Á. M. Prats, J. I. León, and N. Moreno-Alfonso, “Power- Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey”, IEEE Trans. Ind. Electron., vol. 53, no. 4, pp. 1002-1016, August 2006.

[5] W. T. Franke, C. Kürtz and F. W. Fuchs, "Analysis of control strategies for a 3 phase 4 wire topology for transformerless solar inverters," in Proc. IEEE Int. Symp. Ind. Electron., Bari, pp. 658-663, 2010.

An Improved Seven-Level PUC InverterTopology with Voltage Boosting

 ABSTRACT:

 In this brief, a seven-level (7L) improved packed U cell (IPUC) inverter with reduced power electronic components is proposed. The presented IPUC inverter has low voltage stress on switches and is capable of voltage boosting. A new voltage balancing method based on logic form equations is developed for regulating the inherent floating capacitor voltage to half the input DC voltage. The proposed 7L IPUC is compared with other state-of-the-art 7L inverters in terms of number of IGBTs, blocking voltage and driver circuits for attesting its superior merits. The performance of the proposed voltage balancing is verified through a laboratory prototyped 7L IPUC inverter considering varying load conditions and the corresponding results are elucidated.

KEYWORDS:

1.      Logic form equations

2.       Multilevel inverters,

3.      Voltage balancing

4.      Voltage boosting

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

A 7L IPUC inverter topology with reduced power electronics components like switching devices, driver circuits and passive components was presented. The inherent floating capacitor voltage was balanced by using the logic form equations which is independent to the load power factor and its suitable dynamic load variation. The boosting ability of the proposed topology was verified through several experimental tests and the results were presented. Finally, the proposed inverter was benchmarked in terms of number of components against its counterpart topologies. Also, the detailed cost analysis revealed the cost effectiveness of the developed topology. With these attributes, it qualifies as a challenging candidate for medium voltage grid connected photovoltaic system and electric vehicle applications.

REFERENCES:

[1]. Z. Wang, Y. Yan, J. Yang, S. Li and Q. Li, "Robust Voltage Regulation of A DC-AC Inverter with Load Variations via A HDOBC Approach," IEEE Trans. Circuits Syst. II: Exp. Brief doi:10.1109/TCSII.2018.2872330

[2]. T. C. Neugebauer, D. J. Perreault, J. H. Lang and C. Livermore, "A sixphase multilevel inverter for MEMS electrostatic induction micromotors," IEEE Trans. Circuits Syst. II: Exp. Brief, vol. 51, no. 2, pp. 49-56, Feb, 2004.

[3]. M. S. W. Chan and K. T. Chau, "A New Switched-Capacitor Boost- Multilevel Inverter Using Partial Charging," IEEE Trans. Circuits Syst. II: Exp. Brief, vol. 54, no. 12, pp. 1145-1149, Dec, 2007.

[4]. J. S. Mohamed Ali and V. Kumar, "Compact Switched Capacitor Multilevel Inverter (CSCMLI) With Self Voltage Balancing and Boosting Ability," IEEE Trans. Power Electron., doi: 10.1109/TPEL.2018.2871378.

[5]. Y. Ounejjar, K. Al-Haddad, and L. A. Dessaint, “A novel six-band hysteresis control for the packed U cells seven-level converter: Experimental validation,” IEEE Trans. Ind. Electron., vol. 59, no. 10, pp. 3808-3816, Oct, 2012.

A Novel Six-Band Hysteresis Control for the PackedU Cells Seven-Level Converter: Experimental Validation

ABSTRACT:

 In this paper, the authors propose a novel six-band hysteresis technique to efficiently control the seven-level packed U cells (PUC) converter. The proposed PUC combines advantages of the flying capacitor and the cascaded H-bridge topologies. The novel control strategy is proposed in order to insure a good operation of the PUC converter in both inverter and rectifier modes. In case of rectifier operation, the proposed six-band controller is designed to draw a sinusoidal line current (load current in case of inverter operation) with a unity power factor. Harmonics contents of line current (or load current) and rectifier input voltage (or inverter output voltage) are very low which permits the reduction of the active and passive filters ratings resulting on a very high energetic efficiency and a reduced installation cost. The proposed concept was validated through experimental implementation using real-time controller, the DS1103 of dSpace.

KEYWORDS:

 

1.      Active rectifier

2.      Harmonic reduction

3.       Hysteresis

4.      Inverter

5.      Multilevel converters

6.      Packed U cells (PUC)

SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

A novel six-band hysteresis control technique for the seven level PUC converter is presented in this paper. The proposed controller allows a nearly sinusoidal current both in rectifier or inverter operation. The DC link buses voltages are well controlled and track their references even under 100% of load steps. The rectifier input voltage or the inverter output voltage has seven-level voltages which permit to reduce the rating of active and passive filters resulting on a very high energetic efficiency and a reduced installation cost. The good dynamics of the system prove the efficiency of the proposed controller.

REFERENCES:

[1] A. Nabae, I. Takahashi, and H. Akagi, “A new neutral point clamped PWM inverter,” IEEE Trans. Ind. Appl., vol. IA-17, no. 5, pp. 518–523, Sep./Oct. 1981.

[2] L. Yacoubi, K. Al-Haddad, F. Fnaiech, and L.-A. Dessaint, “A DSP-based implementation of a new nonlinear control for a three-phase neutral point clamped boost rectifier prototype,” IEEE Trans. Ind. Electron., vol. 52, no. 1, pp. 197–205, Feb. 2005.

[3] L. Yacoubi, K. Al-Haddad, L.-A. Dessaint, and F. Fnaiech, “A DSP-based implementation of a nonlinear model reference adaptive control for a three-phase three-level NPC boost rectifier prototype,” IEEE Trans. Power Electron., vol. 20, no. 5, pp. 1084–1092, Sep. 2005.

[4] J. Rodriguez, S. Bernet, P. K. Steimer, and I. E. Lizama, “A survey on neutral-point-clamped inverters,” IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 2219–2230, Jul. 2010.

[5] T. Meynard and H. Foch, “Multi-level conversion: High voltage choppers and voltage-source inverters,” in Proc. 23rd Annu. PESC Rec., Jun. 29–Jul. 3 1992, vol. 1, pp. 397–403.