Abstract
This study explores the Whales Optimization Algorithm (WOA)-based PI controller for regulating the voltage and frequency of an inverter-based autonomous microgrid (MG). The MG comprises two 50 kW DGs (solid oxide fuel cells, SOFCs) interfaced using a power electronics-based voltage source inverter (VSI) with a 120-kV conventional grid. Four PI controller schemes for the MG are implemented: (i) stationary PI controller with fixed gain values (Kp and Ki), (ii) PSO tuned PI controller, (iii) GWO tuned PI controller, and (iv) WOA tuned PI controller. The performance of these controllers is evaluated by monitoring the system voltage and frequency during the transition of MG operation mode and changes in the load. The MATLAB/SIMULINK tool is utilised to design the proposed model of grid-tied MG alongside the MATLAB m-file to apply an optimisation technique. The simulation results show that the WOA-based PI controller which optimises the control parameters, achieve 62.7% and 59% better results for voltage and frequency regulation, respectively. The eigenvalue analysis is also provided to check the stability of the proposed controller. Furthermore, the proposed system also satisfies the limits specified in IEEE-1547-2003 for voltage and frequency.
Highlights
The development of modern power electronics with the combination of distributed generation units led to the new notion of microgrid system (MGS)
The simulation results obtained from the proposed controller for regulating voltage and frequency during the transition of the operation mode of MGS are given in Figure 7a,b, respectively
It can be noted that algorithms for Whales Optimization Algorithm (WOA), GWO and PSO for both the cases are applied for offline optimisation, and when the optimal parameters for PI controller are obtained, the attained parameters will be used in the PI controller
Summary
The development of modern power electronics with the combination of distributed generation units led to the new notion of microgrid system (MGS). The coordination between multiple DG units for their power-sharing issue is considered To this end, this study applied a synchronous reference frame technique and an optimal PI controller to compensate the error between the reference and measured values by optimising control parameters to regulate voltage and frequency of an islanded MG. The types of controllers utilized for microgrids (PQ and Vf), the criteria for power-sharing between the grid and MG during the grid-connected mode of MG and performance of MGS during islanding mode have been analysed in [13,14,15] These systems did not consider the tuning of control parameters, which may be required during the transition of MGS operating modes or load variation. The paper is divided into the following sections: the structure of the MG and mathematical modelling of the three-phase grid is discussed in Section 2, the proposed controller details are given in Section 3, simulation results and discussion are presented in Section 4, and Section 5 summarizes of the conclusion of the paper
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