Performance and Analysis of Adaptable PI and SMC for a Hybrid PV-Battery System

This paper proposes adaptable Proportional plus Integral (PI) and Sliding Mode Control (SMC) for a Hybrid System consisting of a solar PV and Battery Energy Storage System (BESS). A boost converter for stepping up the voltage to 400 V and a bidirectional buck/boost converter (BDDC) for charging and discharging of a battery are used. The battery gets charged when the BDDC is in buck mode. During night or during partial shading conditions, BESS operates with the BDDC in boost mode of operation. Stability analysis is performed for the system which ensures good stability margins. Cascaded PI controllers are used for controlling the DC link voltage. A charging circuit is used for buck or a boost mode of operation of BDDC. SMC is used for standalone mode of VSI and cascaded PI controller for grid mode of operation. The controllers work effectively for resistive, inductive and non-linear loads and also during dynamic changes of solar insolation and load variations. Both controllers are found to be good in tracking the reference voltages with less settling time of 1-2 % and steady state errors of less than 2%. The THD of the grid current is found to be 0.086%. The battery SOC is found to be reliable during both charging and discharging operations. Hence reliable power transfer is assured to the loads under all circumstances using these controllers and the control of the system is said to be adaptable.