An-Najah Staff

Time domain performance analysis results of a standalone hybrid system are presented based on commercial wind generator, photovoltaic generator and battery energy storage system. The hybrid system is designed and modelled using Matlab/Simulink/SimPowSys™ environment, a control strategy has been proposed to control the voltage DC bus and the energy flow between the different energy sources. The wind and photovoltaic generators are controlled locally to obtain the maximum power extraction, while battery energy storage system is controlled using specific control strategy depending on the voltage of the DC bus and energy flow. To test the performance of the system three different cases were analyzed; one case is the examination of the system performance when the photovoltaic generator is excluded from the system, the second case excludes wind energy generator while the third case includes all the sources. Each case contains various operating conditions and disturbances of load and weather data. The frequency deviation, stability of DC bus voltage and voltage total harmonic distribution are taken as system performance indexes. The simulation results ensure the effectiveness of the proposed hybrid system control strategy in following up the variations in load demand and weather data, providing the ground for practical realization.

Storage batteries are indispensable in all stand alone solar electric systems (PV power systems). Their efficiencies and life times affect significantly the overall PV system performance and economics. Batteries specified especially for use in PV systems have to be distinguished with standing of very deep discharge rate and high cycling stability. Ordinary batteries being marketed world wide for use in automobile, are mostly not appropriate for PV power systems. The most important characteristics of lead–acid batteries are presented and discussed in this paper. Moreover, the paper illustrates an experimental procedure for developing an algorithm for determining the ampere–hour capacity of batteries operating in PV systems. This algorithm enables determining the state-of-charge of a battery by measuring voltage and electrolyte-specific gravity at definite temperature and is applicable also for large battery storage systems.