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:

 image001

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

EXPECTED SIMULATION RESULTS:

 image002

 Fig. 2. MPPT operation.

       image003

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

image004

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

image005

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

image006

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

image007

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.