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Inertia-less power converters are one of the main obstructions to increase the penetration level of distributed energy resources in the utility grid. The stability of the power system mainly depends on the system inertia. Virtual synchronous machine and synchronverter-based grid-tied inverters have been introduced as a solution to this problem. Here, a modified selfsynchronised synchronverter is introduced to enhance the dynamic response of the active power loop and to limit the injected active/reactive power to the grid. Furthermore, the injected current to the grid is limited during faults employing proportionalresonant-based inner current loop. Feed-forward voltage is implemented in the current control loop to achieve seamless transfer between standalone and grid-connection modes of operation. Extensive simulation and experimental results are obtained to verify the proposed enhanced controller.

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This paper proposes an optimal design of Shunt-Resonance Fault Current Limiter (SRFCL) to enhance the Fault Ride-Through (FRT) capability and improve the transient stability of a grid-connected hybrid PV/wind power system. The design parameters of the SRFCL are optimized by using Particle Swarm Optimization (PSO) technique. The proposed SRFCL topology is designed in such a way that it can provide superior protection capability for limiting the fault current and supporting the grid voltage than the conventional Bridge Fault Current Limiter (BFCL). The effectiveness of the SRFCL in supporting the dynamic performance and improving the transient stability of the hybrid energy system is validated during both symmetrical and unsymmetrical faults in the electrical utility. Moreover, its credibility is evaluated compared with that of the BFCL and the FRT control schemes. Simulations have been performed using the MATLAB/SIMULINK software. The results illustrate that the proposed SRFCL augments significantly the dynamic behavior and the transient stability of the hybrid power system during the fault events. Also, when the optimal SRFCL is employed, the injected active power by the hybrid system and the grid voltage profile are improved considerably under the grid disturbances. Furthermore, the comparison confirms the superiority of the SRFCL performance to both the BFCL topology and the FRT control scheme in every aspect.

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