Reactive power is very essential in maintaining voltage stability of power systems. The voltage constraint at network nodes due to reactive power deficit or insufficiency of reactive power sources restricts active power delivery to the loads and could result in forced load curtailment. Limited attention has been given to reactive power aspect in reliability evaluation of power systems with penetration of renewable energy sources. The reactive power issues become more significant in distributed generation using renewable energy sources such as photovoltaic (PV) Cells, which operate mostly at unity power factor. This paper investigates the effect of reactive power shortage on reliability of power systems with significant penetration of PV cells. The IEEE 14-Bus system is utilized to perform this study. A measure of Expected Energy Not Supplied (EENS) on account of reactive power shortage and voltage violation in network is calculated. By using conventional Monte Carlo simulation, the results are compared with the case without taking into account reactive power and voltage violation constrains. This paper suggests that placement of the PV in the network can greatly reduce active and reactive power shortage during the contingencies. The reactive power is studied here from design and planning perspectives for reliable and stable power system operation when high penetrations of PV energy sources are present.

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Photovoltaic (PV) cell converts sunrays into electrical energy, which has non-linear I-V characteristics. For extracting maximum power from photovoltaic (PV) array for varying environmental conditions, it is necessary to use MPPT tracker. The MPPT consists of DC-DC converter and MPPT algorithm, DC-DC converter is inserted between solar panel and load or battery. The task of MPPT tracker is to match input impedance of the converter and it is equals to the equivalent output impedance of the solar panel to achieve unique point (MPP) where maximum power extracted.The used TL598 based DC-DC converter operates with defined MPPT algorithm. The DC-DC converter output power is controlled by varying its duty cycle to operating at knee voltage level. The novel algorithm is used for efficiently extracts the maximum output power from PV panel with the use of direct control method. The sensing of input voltage and current parameters, which are processed based on P&O algorithm. After finding of MPP, it latched and stops searching and only continuously monitors source voltage. When any change in environmental conditions, the MPPT algorithm again starts searching MPP unique point which is totally based on source voltage information. This approach gets a stable output power at MPP. The algorithm has developed for direct control of duty cycle for DC-DC converter based on TL598. This is simple structure; obtain higher efficiency and reliability as compared to standard methods. The MPPT has capability to propose the technique which has been verified experimentally with a 75-W solar panel for different insolation (incident solar radiation) level and under large signal insolation of level changes. General TermsPV Cell Operating point, Algorithm.