Under normal operating conditions, the flow rate of a solar pump fed by a photovoltaic array follows the variations of the irradiance. However, the flow rate of a photovoltaic pumping system coupled to a water filtration unit should be constant under a constant pressure. So, the combination of solar batteries with a photovoltaic array is required. This paper presents a specific structure of the P & O algorithm for controlling a boost converter inserted between the photovoltaic array without batteries and the driving motor of a centrifugal pump. The simulation results in MATLAB/SIMULINK with ode23t solver show that blocking of the duty ratio of the control pulses of the boost converter enables to maintain a constant output voltage, even if the irradiance varies. Thus, for a duty ratio locked between 0.79 and 0.9, the output voltage of 236 V is obtained, for a flow rate of 1.08 l/s under a pressure of 5.8 bars.
One important problem in the operation of medium voltage networks is the detection of a single-line-to-ground fault in its incipient state, when the fault resistance values are very high. In a medium voltage (MV) distribution network with a neutral grounding resistor (NGR), one of the methods employed to discriminate a single line-to-ground fault is the use of an overcurrent relay with an operating characteristic adjusted according to the effective value of the current flowing through the limiting resistor. In case of a single line-to-ground fault with a high fault resistance value, the correct tripping settings of the protective relay require the precise computation of this current. In comparison to the assumptions made by the models from the literature—the three-phase voltage system of the medium voltage busbars is symmetrical and there are no active power losses in the network insulation—the model proposed in this paper considers the pre-fault zero-sequence voltage of the medium voltage busbars and the active power losses in the network insulation, which is necessary in certain fault conditions where the use of the former leads to unacceptable errors.
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