Converters Techniques For Pv Power Generation In DC Microgrid

The increase in demand for clean,safe and environmentally friendly renewable energy sources,such as PV cells,faces several challenges such as efficiency improvement and large scale applications.Aiming to the PV converters,the main contributions of this dissertation are based on(1)Maximum power point tracking(MPPT)controllers and(2)primary and secondary controller design of parallel Buck converters in DC Microgrid for energy sharing are as follows:· MPPT technique is a method which is used in the photovoltaic power(PVS)to increase the power efficiency.The most important challenges facing conventional MPPT methods are oscillation during steady state and slow power tracking during dynamic state because of getting fixed step size during tracking.The Beta method can handle these challenges using intermediate parameter "Beta" to get variable step size in transient state.However,for higher efficiency,some of the parameters of this method need to be optimized.The main objective to modify the original Beta method is to minimize oscillation in steady state and to tracks rapidly the maximum power in the transient state.Necessary climatic information such as highest,average irradiance and temperature levels are taken from 1-year climatic data set of Karachi city to set up Beta limits.A PLECS model of the modified beta method with the boost converter is proposed and simulated which shows excellent results.· DC Microgrid(MG)is a promising system due to higher efficiency and natural interface to large scale renewable sources.In the hierarchical control of DC Microgrid,the V-I droop control is deployed usually in primary control level for common load sharing between converters.However,conventional droop control causes improper current sharing,voltage variations,and circulating current regulation due to the presence of droop and line resistance between converters.This contribution presents the primary control level design of buck converters in current mode control according to concept of time constant and time delay and,secondary control design for parallel operations in distributed manners by combining methods namely low bandwidth communication(LBC),circulating current minimization techniques,and average voltage/current control.Moreover,different time delays are used for two converters to testify the effects of communication delays on current sharing and voltage restoration.The simulation is done for 2x2.5KWdc parallel buck converters in PLECS environment which shows excellent results in minimizing circulation currents,enhancing proportional current sharing,and restoring the grid voltage.