Discrete model predictive frequency and voltage control of isolated micro-grid in smart grid scenario

In an isolated micro-grid electronically interfaced DG (EI-DG) units should also participate in frequency and voltage control along with synchronous generator based DG (SG-DG) units to ensure power quality and stability of the micro-grid. The conventional way of controlling frequency and voltage is to balance active power and reactive power of the system by implementing droop characteristics (P-f, Q-V) for EI-DG units with PI controllers and automatic generation control (AGC) and automatic voltage regulator (AVR) for SG-DG units. With the advent of smart micro-grids, a centralized control for both frequency and voltage using model predictive controller (MPC) is an alternative to the conventional controllers. The optimization capabilities of MPC make it suitable for frequency and voltage control of micro-grids equipped with fast and reliable communication. This paper investigates the performance of a centralized discrete model predictive controller (DMPC) in an isolated micro-grid with photovoltaic (PV) and diesel generators. The small signal dynamic models of the PV converter and SG-DG are considered in the design of the DMPC. The micro-grid network and loads are represented using steady state power balance equations. The performance of the DMPC is tested using MATLAB software package.