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.

A New Variable Frequency Control of Forty-nine Level Cascaded Packed U-cell Voltage Source Inverter

ABSTRACT:

 Requirement of large number of levels with lower number of switching devices has made asymmetrical converters more popular than the symmetrical ones. Asymmetrical cascaded multilevel inverters (ACMLI) can achieve high efficiency by combining switching devices with different voltage ratings and technologies. The proposed ACMLI cascades two or more units of packed U-Cell (PUC) inverters using two or more isolated DC link supplies. In this paper, one of the PUC unit is controlled using high switching frequency while the other PUCs are operated in a step mode at low switching frequencies, thus operating them in a variable frequency control mode. The cascading of two 7-level PUC inverters with DC link voltage ratios of 1:7 can produce an output voltage with 49 (7x7) levels. The multi-level output voltage waveform is nearly sinusoidal with very low THD content, and the low switching frequency operation leads to lower power dissipation and greater system efficiency. However, each PUC module requires two dc voltage sources. To address this concern, in this manuscript, each PUC module consists of one dc voltage source and one dc bus capacitor. With the cascaded PUC topology and proposed control algorithm, load current and dc bus capacitor voltage control is achieved simultaneously. The proposed converter and its control technique lead to the breaking of the design trade-off rule between switching frequency (efficiency) and filter size. This is very useful in various applications such as Uninterruptible Power Supplies (UPS), and grid-tie inverters. The converter and its control technique are simulated using MATLAB/Simulink software and simulation results for both open loop and closed loop are discussed. Hardware results are obtained by developing a 1-KW experimental prototype. Simulation and experimental results confirm the usefulness and effectiveness of the proposed topology and its control technique. 

KEYWORDS:

1.      Asymmetric cascaded multilevel inverters

2.      Total Harmonic Distortion

3.      Variable frequency control

4.      Packed U-Cell inverters

5.      Low switching frequency

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper presented a cascaded Packed U-Cell inverter with forty-nine output voltage levels offering a reduced switch count solution. Only two auxiliary capacitors along with two isolated dc voltage sources are used to achieve forty-nine levels in the output voltage waveform. Between the two cascaded PUCs, one cell operates at high switching frequency (2 kHz) and other unit is operating at seven time the fundamental frequency (350 Hz). DC link voltage ratio of the two PUCs is kept at 1:7 to achieve the maximum forty-nine level output voltage. Detailed explanation of level formation and individual PUC output voltages are also discussed. Presented control algorithm achieves dc bus capacitor voltage and load current control simultaneously. Simulation results are discussed in detail for both open loop and closed loop performances. Accurate and robust control of dc bus capacitor control is achieved during load current variation as shown in transient response of the system. Experimental results validate voltage levels formation in individual PUC module and formation of resultant 49 – levels in output voltages. THD spectrum of load voltage and load current are also presented (in both simulation and experimental results), which verify the superior THD performance.

REFERENCES:

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

[2]. L.G. Franquelo, J. Rodriguez, J.I. Leon, S. Kouro, R. Portillo, M.M. Prats, “The age of multilevel converters arrives”, IEEE Ind. Electro. Mag., vol. 2, no. 2, pp. 28–39, Jun. 2008.

[3]. S. Kouro, M. Malinowski, K Gopakumar, J. Pou, L.G Franquelo, B. Wu, J. Rodriguez, M.A. Perez, J.I. Leon, "Recent advances and industrial applications of multilevel converters," IEEE Transactions on Ind. Elect., vol.57, no.8, pp.2553-2580, Aug. 2010.

[4]. 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. 1981.

[5]. S. Payami, R. K. Behera and A. Iqbal, "DTC of Three-Level NPC Inverter Fed Five-Phase Induction Motor Drive with Novel Neutral Point Voltage Balancing Scheme," in IEEE Transactions on Power Electronics, vol. 33, no. 2, pp. 1487-1500, Feb. 2018.

A New 7L-PUC Multi-Cells Modular MultilevelConverter for AC-AC and AC-DC Applications

ABSTRACT:

In this paper, a new cell based Modular Multilevel Converter (MMC) for AC-AC and AC-DC applications is presented. The new topology makes use of an efficient Packed U Cells (PUC) structure to form the Multi-Cells Modular Multilevel Converters (M3C). It is a member of MMC root family, with extended operational capability covering therefore AC-AC and AC-DC modes of operation. A dynamic model of the PUC and the single phase M3C will be used along with predictive control method to validate the effectiveness of different operation modes of the converter.

KEYWORDS:

1.      Modular Multilevel Converter (MMC)

2.      Multi-Cells Modular Multilevel Converters (M3C)

3.      Packed U-Cells

4.      Single phase AC-AC and AC-DC power converter

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

A new efficient multilevel cell topology has been introduced to the M3C family. The increased cell terminal voltage levels bring more smoothness to the arm controlled voltages, thus increasing the voltage levels to component ratio. Wide range of operating modes were tested, showing fast dynamic response to variations in reference signals. Model predictive control proved effectiveness against transient output references and kept good performance with capacitor parameter variations.

REFERENCES:

[1] H. Abu-Rub, M. Malinowski, and K. Al-Haddad, Power Electronics for Renewable Energy Systems, Transportation and Industrial Applications: John Wiley & Sons, 2014.

[2] B. Singh, A. Chandra, and K. Al-Haddad, Power Quality: Problems and Mitigation Techniques: John Wiley & Sons, 2015.

[3] R. Marquardt, "Stromrichterschaltung mit verteilten Energiespeichern und Verfahren zur Steuerung einer derartigen Stromrichterschaltung," Patentschrift DE 101 03 031 B4 Patent, 2001.

[4] A. Lesnicar and R. Marquardt, "A new modular voltage source inverter topology," presented at the European Power Electronics Conference (EPE), Toulouse, France, 2003.

[5] M. Glinka and R. Marquardt, "A new AC/AC multilevel converter family," IEEE Transactions on Industrial Electronics, vol. 52, pp. 662- 669, 2005.