Backstepping Control of Smart Grid-Connected Distributed Photovoltaic Power Supplies for Telecom Equipment

ABSTRACT:

Backstepping controllers are obtained for distributed hybrid photovoltaic (PV) power supplies of telecommunication equipment. Grid-connected PV-based power supply units may contain dc–dc buck–boost converters linked to single-phase inverters. This distributed energy resource operated within the self consumption concept can aid in the peak-shaving strategy of ac smart grids. New backstepping control laws are obtained for the single-phase inverter and for the buck–boost converter feeding a telecom equipment/battery while sourcing the PV excess power to the smart grid or to grid supply the telecom system. The backstepping approach is robust and able to cope with the grid nonlinearity and uncertainties providing dc input current and voltage controllers for the buck–boost converter to track the PV panel maximum power point, regulating the PV output dc voltage to extract maximum power; unity power factor sinusoidal ac smart grid inverter currents and constant dc-link voltages suited for telecom equipment; and inverter bidirectional power transfer. Experimental results are obtained from a lab setup controlled by one inexpensive dsPIC running the sampling, the backstepping and modulator algorithms. Results show the controllers guarantee maximum power transfer to the telecom equipment/ac grid, ensuring steady dc-link voltage while absorbing/injecting low harmonic distortion current into the smart grid.

KEYWORDS:

  1. Backstepping
  2. Buck–boost converter
  3. Dc/ac converter
  4. MPPT
  5. Self-consumption
  6. Smart grids

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

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Fig. 1. PV distributed hybrid self-consumption system and telecom load.

EXPECTED SIMULATION RESULTS:

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 Fig. 2. MPPT operation.

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Fig. 3. Voltage and current waveforms when there is a change from inverter to rectifier.

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Fig. 4. (a)Voltage and current waveforms when there is a change from inverter to rectifier. (b) Center part zoom of (a).

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Fig. 5. Voltage and current waveforms when the load requires 25 W.

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Fig. 6. Voltage and current waveforms when the load requires 62 W.

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Fig. 7. DC–AC converter input power.

 CONCLUSION:

This paper proposes a novel backstepping controller for a PV panel feeding a buck–boost converter, and dc linked to a telecom load and a single-phase ac–dc converter connected to a smart grid, configuring a subset of a distributed hybrid photovoltaic power supply for telecom equipments within the self-consumption concept. This setup absorbs/injects nearly sinusoidal (THD = 1.6%, lower than the 3% required by the standards) grid currents at near unity power factor and the self consumption can contribute to the smart grid peak power shaving strategy.

New nonlinear backstepping control laws were obtained for the input voltage of the buck–boost converter, thus achieving MPP operation (MPPT efficiency between 98.2% and 99.9%) and for the dc–ac converter regulating the dc telecom load voltage and controlling the ac grid current. All the control laws, fixed frequency converter modulators, voltage and current sampling, and grid synchronization have been implemented using a low-cost dsPIC30F4011 microcontroller.

Obtained experimental results show the performance of the PV self-consumption system using the backstepping control method. Results show the system dynamic behavior when the dc–ac converter changes operation from inverter to rectifier to adapt itself to the telecom load requirements. The robustness of the control laws has been tested as well. Capacitance of real capacitors can vary almost ten times around the rated value, while inductances can vary from 30% to nearly 300% of the rated value.

 REFERENCES:

[1] N. Femia, G. Petrone, G. Spagnuolo, and M. Vitelli, Power Electronics and Control Techniques for Maximum Energy Harvesting in Photovoltaic Systems. Boca Raton, FL, USA: CRC Press, 2013.

[2] A.Maki and S. Valkealahti, “Effect of photovoltaic generator components on the number of MPPs under partial shading conditions,” IEEE Trans. Energy Convers., vol. 28, no. 4, pp. 1008–1017, Dec. 2013.

[3] Epia Org. (2013, Jul.). Self-consumption of PV electricity—Position paper. [Online]. Available:http://www.epia.org/fileadmin/user_upload/Position_Papers/Self_and_direct_consumption_-_position_paper_-_final _version.pdf

[4] SunEdison. (2011, Nov.). Enabling the European consumer to generate power for self-consumption. [Online]. Available: http://www. sunedison.com/wps/wcm/connect/35bfb52a-ec27-4751-8670-fe6e807e8063/SunEdison_PV_Self  consumption_Study_high_resolution_%2813_ Mb%29.pdf?MOD=AJPERES

[5] A. Nourai, R. Sastry, and T.Walker, “A vision & strategy for deployment of energy storage in electric utilities,” in Proc. IEEE Power Energy Soc. Gen. Meeting, 2010, pp. 1–4.

An Efficient Modified CUK Converter with Fuzzy based Maximum Power Point Tracking Controller for PV System

ABSTRACT:

To improve the performance of photovoltaic system a modified cuk converter with Maximum Power Point Tracker (MPPT) that uses a fuzzy logic control algorithm is presented in this research work. In the proposed cuk converter, the conduction losses and switching losses are reduced by means of replacing the passive elements with switched capacitors. These switched capacitors are used to provide smooth transition of voltage and current. So, the conversion efficiency of the converter is improved and the efficiency of the PV system is increased. The PV systems use a MPPT to continuously extract the highest possible power and deliver it to the load. MPPT consists of a dc-dc converter used to find and maintain operation at the maximum power point using a tracking algorithm. The simulated results indicate that a considerable amount of additional power can be extracted from photovoltaic module using a proposed converter with fuzzy logic controller based MPPT

KEYWORDS:

 modified Cuk Converter

Photovoltaic System

Maximum Power Point Tracker

Fuzzy Logic Controller

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

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Figure 1: Simulation diagram for the proposed converter

EXPECTED SIMULATION RESULTS:

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(a)

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(b)

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(c)

Figure 2: Output of Solar Irradiation at 500 watts / m2 (a)

Current, (b) Voltage, (c) Power

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(a)

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(b)

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(c)

Figure 3: Output of Solar Irradiation at 1000 watts / m2 (a)

Current, (b) Voltage, (c) Power

CONCLUSION:

The proposed modified cuk converter was simulated in MATLAB simulation platform and the output performance was evaluated. Then, the mode of operation of proposed converter was analyzed by the different solar irradiation level. From that, output current, voltage and power were considered. For evaluating the output performance, the proposed modified cuk converter output was tested with PV system. From the testing results, the output power of the modified converter efficiency and the efficiency deviation were analyzed. The analyses showed that the proposed modified cuk converter was better when compared to conventional cuk converter and boost converter. Experimental setup has been done to prove the effectiveness of the proposed system.

REFERENCES:

  1. Singh R & Sood Y R, Transmission tariff for restructured Indian power sector with special consideration to promotion of renewable energy sources, IEEE Region 10 Conference, TENCON, (2009), 1 – 7.
  2. Xia Xintao & Xia Junzi, Evaluation of Potential for Developing Renewable Sources of Energy to Facilitate Development in Developing Countries, Asia-Pacific Power and Energy Engineering Conference (APPEEC), (2010), 1 – 3.
  3. Hosseini R & Hosseini N & Khorasanizadeh H, An experimental study of combining a photovoltaic system with a heating system, World Renewable Energy Congress, 8 (2011), 2993-3000.
  4. Shakil Ahamed Khan & Md. Ismail Hossain, Design and Implementation of Microcontroller Based Fuzzy Logic Control for Maximum Power Point Tracking of a Photovoltaic System, IEEE International Conference on Electrical and Computer Engineering, Dhaka, (2010), 322-325.
  5. Pradeep Kumar Yadav A, Thirumaliah S & Haritha G, Comparison of MPPT Algorithms for DC-DC Converters Based PV Systems, International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering, 1 (2012), 18-23.