Mohammad S. Widyan
Photovoltaic generator, maximum power point tracking, DC machines dynamics, power control unit
In this paper, modelling, simulations and operational performance characteristics of a hybrid-powered permanent-magnet DC (PMDC) motor for pumping applications are investigated. The hybrid energy system comprises fuel-driven DC shunt generator and photovoltaic (PV) array. The PV generator is integrated to the output of the DC generator through DC–DC buck-boost switch mode converter. The main idea of incorporating the inexhaustible PV generator is to reduce the overall fuel consumption and CO2 emissions of the conventionally powered DC generator and therefore the system has been equipped with a maximum power point tracking (MPPT) controller such that to be able to extract the maximum energy available in the PV array at all solar irradiance levels. The MPPT technique of the PV generator is the open-circuit voltage method via adjusting the duty cycle of the DC–DC converter. The stability of the system operating point is studied via eigenvalues of the linearized system at various loading conditions. The dynamics of the PV generator is included by considering the nonlinearities of its terminal characteristics. Based on the complete nonlinear dynamical mathematical model, time domain simulations after successive step changes on the solar irradiance levels at given pumping capacity and after successive step changes on the motor pumping capacities at given solar irradiance levels are conducted. The steady-state torque-speed characteristics of the PMDC motor at various operating conditions have been presented and compared. It is concluded that hybrid powering the PMDC motor for pumping applications through DC shunt and PV generators is possible at all realistic loading conditions, robust as it can withstand various practical disturbances and can reduce the total fuel consumption and CO2 emissions.
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