Adaptive inertia emulation control for high-speed flywheel energy storage systems

Low-inertia power systems suffer from a high rate of change of frequency (ROCOF) during a sudden imbalance in supply and demand. Inertia emulation techniques using storage systems, such as flywheel energy storage systems (FESSs), can elp to reduce the ROCOF by rapidly providing the needed power to balance the grid. In this work, a new adaptive ontroller for inertia emulation using high-speed FESS is proposed. The controller inertia and damping coefficients vary using a combination of bang–bang control approaches and self-adaptive ones, to simultaneously improve both the ROCOF and the frequency nadir. The performance of the proposed adaptive controller has been initially validated and compared with several existing adaptive controllers by means of offline simulations, and then validated with experimental results. The proposed controller has been implemented on a real 60 kW high-speed FESS, and its performance has been evaluated by means of power hardware-in-the-loop (PHIL) testing of the FESS in realistic grid conditions. Both Simulations and PHIL testing results confirm that the proposed inertia emulation control for the FESS outperforms several previously reported controllers, in terms of reducing the maximum ROCOF and improving the frequency nadir during large disturbances

Robust Primary Control of Microgrids for Parametric and Topological Uncertainties: A Quest for Resilience

In this paper, a robust droop-based control structure is developed in primary level of a hierarchical control scheme for robust performance and robust stability against parametric and topological uncertainties to 1) improve the robust stability and robust performance 2) resolve drawbacks of previously reported methods. Considering droop control scheme, the conventional hierarchical control structure is developed and the effectiveness of the proposed control scheme is investigated considering parametric and topological uncertainties. For the sake of drawing a picture to address how we can realize a resilient microgrid including a hierarchical control structure and providing enough robustness against mentioned uncertainties, signal disturbances, and different types of nonlinearity, some special recommendations are also provided. Finally, to prove the usefulness of the proposed controller, simulation studies are done on a microgrid which includes several distributed generation units with local loads.©2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.fi=vertaisarvioitu|en=peerReviewed

DC Fault Current Analyzing, Limiting, and Clearing in DC Microgrid Clusters

A new DC fault current limiter (FCL)-based circuit breaker (CB) for DC microgrid (MG) clusters is proposed in this paper. The analytical expressions of the DC fault current of a bidirectional interlink DC/DC converter in the interconnection line of two nearby DC MGs are analyzed in detail. Meanwhile, a DC fault clearing solution (based on using a DC FCL in series with a DC circuit breaker) is proposed. This structure offers low complexity, cost, and power losses. To assess the performance of the proposed method, time-domain simulation studies are carried out on a test DC MG cluster in a MATLAB/Simulink environment. The results of the proposed analytical expressions are compared with simulation results. The obtained results verify the analytical expression of the fault current and prove the effectiveness of the proposed DC fault current limiting and clearing strategy