Dynamic voltage stability study of a stand-alone photovoltaic microgrid supplying an electric mill in Benin rural zone

Nowadays, the search for quality electric power in the use of renewable electric energy is a great concern for all users at all levels. In this paper, we studied the dynamic stability of the amplitude and frequency of the voltage of a stand-alone photovoltaic microgrid feeding an electric mill driven by a three-phase induction motor (IM) in the rural area of the commune of Covè in Benin. The identification of the meteorological data of the said area allowed us to dimension and model in Matlab/Simulink all the components of the system. The results showed that the dynamic load constituted by the IM with the variation of its load torque severely disturbs the amplitude and frequency of the supply voltage. The Fast Fourier Transform (FFT) analysis showed that the variation of the total harmonic distortion (THD) is a function of the load torque of the IM. This load torque is that of the mill which varies according to the flow of the product (grain for example) to be crushed. We have voltage dips of more than 90% and THD of more than 68%. The installation of an anti-harmonic filter or the addition of an inertial source like the windmill is supposed to improve this voltage instability.