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This paper proposes a mathematical model to obtain an improved analytical determination of the maximum power point (MPP) of silicon photovoltaic panels. The MPP is obtained by considering the 5-parameter PV model to calculate the derivative of the PV panel output current with respect to its output voltage including the shunt and series resistors. Theoretical results are compared to experimental field data to demonstrate the accuracy improvements with respect to lab measurements. Finally, with this model is possible also to observe and predict more accurately the efficiency of photovoltaic panels for the various conditions of load, temperature and solar radiation.

This paper presents a new configuration for a wind energy conversion system (WECS) with variable speed, using a squirrel cage induction generator (SCIG) for standalone energy system applications. The Proposed configuration utilizes converters with reduced power rating, operates with MPPT to maximum wind energy extraction, uses battery bank for energy storage and can operate with non-linear and unbalanced loads. Energy storage characteristic is desirable for wind energy conversion systems isolated from the mains since an energy interruption does not stop of the entire system. Also, the power rating of the converters is reduced compared to the generator and load power rating due to the low power requirements of the power converters to SCIG excitation control and to supply the load. It is presented also the whole proposed WECS and the system operation modes according the turbine speed. It is presented also the whole proposed system and the system operation modes according the turbine speed. The simulation of the proposed WECS is performed in conjunction with the dynamic wind turbine model of 1 kW and the results confirm the effectiveness to supply unbalanced and non-linear loads, the converters power rating reduction and operation with variable turbine speed. Simulation results show the effectiveness of the system to supply unbalanced and non-linear stand alone loads.Index Terms -Wind energy conversion system, SCIG, stand-alone energy system, reduced converter power rating.

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