Development of hybrid controller for photovoltaic based DC-DC boost converter in DC grid connected applications

Abstract

Solar energy source is one of the most promising energy sources in nature, but the output power generated by photovoltaic (PV) devices which converts sun's light energy to electrical energy, is a nonlinear function of the external environment. To improve the performance of PV devices in such cases, design of maximum power point tracking (MPPT) function is more important. In addition to it, in DC grid connected applications of PV system, the grid voltage fluctuates due to load disturbances, so a voltage controller is needed to maintain stable dc output. The aim of this work is to develop a hybrid controller for PV based DC-DC boost converter in DC grid connected applications. The hybrid controller proposed here consists of MPPT controller and a voltage regulator. The MPPT controller uses random search method to track the global maximum power point and voltage regulating action is performed by using PID controller, which is used to maintain stable dc output irrespective of grid fluctuations. In the proposed system, the output of PV array fed DC-DC boost converter B1 is connected to boost converter B2 whose output is fed to DC grid. While boost converter B1 will take care of MPPT, the other will function as voltage regulator thus meeting dual requirement of both MPPT and voltage regulation of DC bus with the help of independent duty ratio control of DC-DC boost converters. Modeling and simulation of proposed system is performed in MATLAB/SIMULINK environment. The results presented show that the controller for the individual DC-DC boost converters are able to maintain the desired DC link voltage apart from harvesting maximum power from the solar PV irrespective of variation in the insolation at the input and load variation.