Synchronverter With Emulation Based Current Control to Improve Small Signal Stability in Islanded Microgrid

Among various inertia based grid-forming control techniques, synchronverter (SV) has emerged as a promising solution. In islanded mode of operation, the SV regulates frequency and voltage, enabling active power sharing. However, SV control employed in islanded microgrid experiences voltage sensitivity issues, leading to current distortions thereby causing active and reactive power oscillations under the influence of inductive and constant power load (CPL). Additionally, disproportionate active power sharing occurs upon local frequency restoration. This paper proposes a current controlled synchronverter (CCSV) that offers fast current control by emulating the LCL filter equations. This reduces distortion in currents offering a straight forward approach for balanced as well as unbalanced loading conditions. As a result, active and reactive power oscillations are eliminated, and active power sharing is enhanced upon local frequency restoration. For islanded microgrid with multiple converters, the synchronverter parameters were optimised to offer improved stability, reduced frequency deviation, and better performance under different loading conditions. The proposed method is compared with some existing techniques, and the performance of the CCSV is tested by simulating microgrid test system using RTDS (Real Time digital simulator) and evaluating small signal stability. The proposed method is also tested under unbalanced loading conditions, demonstrating effective mitigation of unbalance in bus voltages, which is essential for constant power loads. Furthermore, controller Hardware in loop (CHIL) testing, along with comprehensive analysis and comparisons are conducted to validate the effectiveness of the proposed CCSV.