Fault-tolerant virtual synchronous generator control of inverters in synchronous generator-based microgrids

Virtual synchronous generator (VSG) control approach which mimics the behavior of conventional synchronous generator (SG) is an attractive solution to integrate low inertia inverter-based distributed energy resources into SG-based microgrids (MGs). As a result, parallel operation of VSGs and SG is a common practice to guarantee the stability of the MGs. Induction motors (IMs) with heavy reactive power demand during acceleration in post-fault condition heighten the risk of instability of SG-based MGs in islanding subsequent to faults. In this paper a novel VSG control system based on the concept of VSG is developed for inverters operating in parallel with SG to improve the voltage and frequency stability of MG with high penetration of IM loads during faults. For this purpose, a fault tolerant enhancement (FTE) module is added to the core of the VSG control system. Accurate reference power tacking in grid-connected (GC) mode, the capability of forming a MG in stand-alone (SA) mode when the SG is out of service and resistance against the grid disturbance are other merits of employing the proposed control system. A current limiting strategy is adopted to restrict the inverter current during fault without devastating control system operation and causing instability. Moreover, a systematic approach for design of a robust dual loop multi-input multi-output (MIMO) control system for inverters is proposed. A new dynamic modeling approach is developed in order to analyze the behavior of the proposed control system and design control parameters. Extensive simulations conducted in MATLAB/Simulink are used to substantiate the effectiveness of the proposed control. It is concluded in simulations that, unlike conventional VSG control, the proposed VSG maintains the voltage and frequency stability of the overall MG in islanding subsequent to a 140 ms fault. Furthermore, the proposed MIMO control and associated current limiting strategy improves the stability when a 140 ms fault occurs. Simulations, besides, confirms the accuracy of the proposed dynamic modeling procedure.

Automated summary

A novel VSG control system based on the concept of VSG is developed to improve the voltage and frequency stability of MG with high penetration of IM loads during faults in islanding subsequent to faults. The proposed control system includes a fault tolerant enhancement (FTE) module, a current limiting strategy, and a robust dual loop multi-input multi-output (MIMO) control system for inverters. Extensive simulations conducted in MATLAB/Simulink confirm the effectiveness and accuracy of the proposed control system.