MODEL PREDICTIVE CONTROL FOR PARALLEL OPERATION OF CONVERTERS IN DC MICROGRID

Abstract

The attention of researchers and power electronics industry is diverted towards the DC Microgrid in recent years due to large penetration of renewable energy sources (RES), in order to reduce greenhouse gas (GHG) emission and achieve energy security. AC bus voltage fluctuation, changing load, power quality, frequency and equal power sharing between different distribution generations (DGs) are main issues in AC system. Linear controllers which are used for the basic control for the power converters face many problems like extra numbers of power switches, modulation techniques, tuning of gain parameter is time consuming, stability issues and slow dynamic response. In order to mitigate the afore-mentioned issues, Model predictive control (MPC) is used for the control of DC DC converters. MPC uses mathematical modelling of the system to forecast the future system behaviour from the current system state. This generates an optimal control sequence. Finally, the optimal control action to be applied to the system. The main advantage of MPC is that constraints and non-linearity’s can be included in the optimization and easy to understand. This thesis proposed an MPC based DC microgrid system which provides continuous power to the load on DC bus in order to enhance the system stability. Thus, parallel operation of the DC converters is very effective solution for it. DC droop control for parallel operation are investigated for assurance of the accurate power-sharing among DG units. To satisfy the performance of the proposed model predictive controller under different conditions (single DG with single load, single with changing single DG, parallel DG, s with single and parallel DG, s with changing load) simulations are showed by using MATLAB/Simulink. This work shows good performance and fast transient response as compared to linear control. This thesis introduces a model predictive controller (MPC) to ensure power sharing and regulate dc bus voltage in dc microgrids with constant load and changing load reviewed and their problems are discussed.