Development of inverter control methods for microgrid applications

With renewable energy source (RES) increasingly connected to the load and the electrical grid through power electronic devices, micro grids (MGs) have to provide adequate ancillary services to deal with various challenges such as active and reactive power oscillations, active and reactive power sharing, fault ride through capability and overcurrent problem. Therefore, control of single or parallel operated power electronic based RES is a significant research subject and critical for the MGs. In this regard, aim of this thesis is to improve control strategies for single three-phase and parallel three-phase inverter topologies in island and grid connected modes in MGs applications. In this thesis, various control strategies such as flexible control, voltage support control, sequence-based droop control and predictive current control have been proposed to; i) improve the interaction of the inverter topologies with the grid, ii) increase the power/current quality, iii) increase the voltage stability, iv) perform current, voltage and frequency control, v) guarantee overcurrent protection, vi) eliminate active and reactive power oscillations, vii) provide voltage support, viii) ensure reactive power support and viii) provide power sharing between parallel inverters. The effectiveness and accuracy of the proposed control strategies are supported by detailed simulation studies and numerical analysis using PSCAD/EMTDC and MATLAB software programs. Also, the effectiveness of the proposed methods has been verified with real-time results using DSP-based PIL.