Battery Energy Storage System converter control: Virtual Generator application for fault conditions.

Description

The growing need of integrate renewable energies, such as wind and solar has been driven by the necessity of reducing air pollutant, reducing greenhouse gases emissions, improv- ing public health and having energy supply diversication. This need of sustainability cannot exclude the necessity to guarantee reliability and stability of the electrical power system, and more specically Microgrid systems, both in normal operating scenarios and during unexpected events such as unintentional islanding or fault events. For this rea- son renewable generation as to be support by intelligent system such as Battery Energy Storage Systems in order to have an energy reserve able to follow the oscillations of the renewable energies and to guarantee a stable control of voltage and frequency. These energy sources are typically connected via power electronics in order to have rapid re- sponse and degree of freedom to implement several control techniques. But the increase in the interfacing of energy sources with inverters has contributed to the reduction of system inertia and this aspect has to be investigated. This thesis proposes a new control algorithm for Battery Energy Storage System able to provide inertial contribution in order to mimic the behaviour of a synchronous generator and then a new approach to adapt this algorithm to fault condition which can cause severe instability of the Micro- grid. After a rst introduction chapter, Chapter 2 presents the new Virtual Synchronous Gen- erator control algorithm and some simulations carried out with the dedicated simulation software DIgSILENT PowerFactory® show the correct dynamic behaviour in normal operating scenarios. Then Chapter 3 deals with the modication of the proposed control scheme in order to properly manage symmetrical faults in islanded and grid connected conguration with a particular focus on the resynchronisation problem. Chapter 4 pro- poses a complete set of simulations in order to show the excellent results obtained in this research eld. Overall conclusions and nal remarks are reported in Chapter 5. This Ph.D. thesis is an outcome of a scientic research that I have conduct during the three years long Ph.D. program, in collaboration with and founded by Hitachi Power Grids.

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