A research into the operation of a system of electric energy accumulation as part of a cyber-physical real time simulation facility

Abstract

Introduction: the frequency and capacity control, as well as the maintenance of electric energy systems rely on the choice of the items of equipment that comprise a particular electric energy system. Generators are the core items of equipment comprising traditional electricity systems, while in off-grid electricity systems this function is assumed by the power-driven converter equipment coupled with energy accumulation systems. The main problem of these systems consists in a fast response generated by the power-driven converter equipment to the changing environment. Excessively fast responses, given by the controllers, make the whole off-grid electricity system unstable.Methods: the resolution of the problem of an unstable off-grid electricity system requires the use of algorithms for the control over inverters and frequency converters, designed according to the principle of a virtual synchronous machine that applies voltage and frequency droops. The model of an electricity system has been produced. It has six key elements: a basic balancing inverter, two generators, lithium-oil battery simulation, an interface converter and a real time digital simulator (RTDS). The model was used to perform an experiment to implement two-way data transmission from RTDS to converting facilities and to verify the performance capability of the algorithm and the electricity system as a whole.Results and discussion: as a result of this experiment, the contact was made between RTDS, Generator 1, Generator 2 and the basic balancing inverter through interface converters. This electricity system is resilient and failure-free.Conclusion: data communication was organized between the real time module of digital simulation and Generator 2. Control commands were delivered from the digital simulation module through interface converters, and their execution monitoring was used as a feedback. The operation of grid-forming and grid-filling converters of a self-contained electricity system was stand tested at the MIPT Centre for Engineering, and optimization algorithm performance results were obtained in respect of a battery used in the course of the application of virtual synchronous machines.