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:
Fig.
1. PV distributed hybrid self-consumption system and telecom load.
EXPECTED SIMULATION RESULTS:
Fig.
2. MPPT operation.
Fig.
3. Voltage and current waveforms when there is a change from inverter to
rectifier.
Fig.
4. (a)Voltage and current waveforms when there is a change from inverter
to
rectifier. (b) Center part zoom of (a).
Fig.
5. Voltage and current waveforms when the load requires 25 W.
Fig.
6. Voltage and current waveforms when the load requires 62 W.
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.
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