ABSTRACT:
Power
quality is highlighted as an important parameter in modern power systems.
Moreover, grid-connected photovoltaic power plants are increasing significantly
in size and capacity. Elsewhere, due to the progressive integration of
nonlinear loads in the grid, the principal role of a Solar Energy Conversion
System (SECS) is not only to capture the maximum power from solar but, also to
ensure some ancillary services and improve the quality of power. This paper
presents a novel strategy dedicated to improve the management of active power generation,
reactive power compensation and power quality of a SECS, while guaranteeing the
possibility of exploiting the full capacity of the Power Conditioning System
(PCS) and the PhotoVoltaic System (PVS). The proposed control algorithm is
applied to a large scale PVS connected to the grid through a cascade of a DC-DC
converter and a PWM inverter. This control strategy manages the SECS function’s
priorities, between main active power generation, reactive power compensation
and active filtering in such a way to guarantee a smooth and stable DC voltage
and ensure a sinusoidal grid current. Top priority is given to the active power
production over power quality improvement. Then, priority is given to reactive
power compensation over mitigation of current harmonics absorbed by the
non-linear load connected to the Point of Common Coupling (PCC). Moreover, the whole
system upper limits of active and reactive powers have been determined in the (PQ)
power plane on the basis of PVS available power, converters rated power and DC
bus voltage smoothness and stability. Finally, a control procedure dedicated to
the calculation of the inverter current commands is proposed in order to
exploit the full capacity of the SECS and respect the determined power limits.
Simulation results confirm the effectiveness and the performance of this
control strategy and prove that the SECS can operate at its full power whilst the
power quality can be improved by reactive power compensation and active filtering.
KEYWORDS:
1. Power
decoupled control
2. Harmonic
currents
3. Power
quality
4. Active
filtering
5. Reactive
power compensation
6. SECS
full power exploitation
SOFTWARE:
MATLAB/SIMULINK
CONCLUSION:
In
this paper, a novel strategy has been proposed to manage and improve the power
quality of a grid connected large scale PVS. More accurately, fuzzy logic
controllers have been used to guarantee a decoupled control of active and
reactive powers injected into the grid. The PWM inverter is controlled in such
a way to manage between active power production and power quality improvement
without exceeding the whole system power capacity. The proposed priority
control block gives top priority to active power production, then reactive
power compensation and finally active filtering. The power capability of the whole
system has been delimited in the (PQ) power plane (on the basis of the PVS
available power, the power electronics converters rated power and the DC bus
voltage smoothness and stability) and fully exploited without over-rating, by
the calculation of an appropriate portion of current commands in order to
ensure a better active filtering quality and keep the inverter current under
its limit value corresponding to the whole system power capacity. Simulation
results show the effectiveness and the performance of the proposed approach in terms
of power generation, reactive power compensation and active filtering.
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