Control algorithm for coordinated operation of wind-solar microgrid standalone generation system

ABSTRACT

In this paper, a wind-driven self-excited induction generator (SEIG) combining solar photovoltaic (SPV) and battery storage has been successfully demonstrated. A second-order sequence filter-based frequency locked loop (SOSF-FLL) control is implemented for operating the voltage source converter (VSC). The SOSF-FLL method is designed by replacing two second-order low pass filter (LPF) pure integrators with two reduced order generalized integrators (ROGIs). The SOSF-FLL has a nonlinear control feedback system. The major contributions in this study include: 1. Implementation of SOSF-FLL control to generate reference source currents for VSC and evaluate the amplitude of load current component under intermittent condition of renewable energy sources (RESs) and nonlinear load, 2) The control algorithm with VSC performs numerous functions such as voltage/frequency regulation, load leveling, harmonic reduction, active/reactive power compensation and reduces the overall power quality problems, 3) Through DC-link voltage management, a bidirectional converter (BDC) with battery storage optimizes the best power flow to provide power balancing between the sources and the unbalanced load, 4) Under diverse operating situations, an incremental conductance (INC)-based maximum power point tracking approach with BDC control provides quick system convergence and support frequency. Moreover, a comparison is carried out between SOSF-FLL control and conventional control algorithms. The settling time of the proposed control is very less than one cycle (20 ms) within 2% described limit, whereas the conventional control algorithms show oscillations of more than 5% during the load dynamics. Despite the load current THD 24.41%, the proposed control is able to obtain supply current THD at 4.23%, which is less than 5% as per IEEE-519 standard. The proposed microgrid (MG) is constructed in MATLAB/Simulink and experimental prototype environment, and its dynamic response is investigated under dynamic conditions of RESs and nonlinear load conditions.

KEYWORDS:

• Battery system
• bi-directional converter
• harmonic analysis
• microgrid
• Second-order sequence filter-based frequency locked loop

Disclosure statement

No potential conflict of interest was reported by the author(s).