Gómez Anccas, Edgar Diego

Utilizing multi-energy renewable microgrids is a promising prospect for decentralized electric power generation. To form a multi-energy microgrid and integrate different renewable energy sources, grid-forming inverters are the core elements. Therefore, their performance has to be tested and validated to increase the quality and reliability of the power supply. The present paper investigates the suitability of a specifically designed and implemented grid-forming inverter as the central component in such microgrid systems. Quality of black-start, frequency and voltage regulation, fast transient response, energy efficiency, low harmonic distortion, proper power factor control, synchronization and phase alignment for integration of renewable energy sources and energy storage devices such as photovoltaics and lithium-ion battery bank, respectively, fault-ride through capability, and resilience to fluctuations imposed by loads are the main features that have been tested and validated for a laboratory-scale grid-forming inverter. The study focuses on the parameters essential for ensuring the reliable and efficient operation of the inverter in dynamic and diverse energy environments, especially its adaptability to varying load profiles and its resilience towards intermittent energy inputs. The findings from this performance evaluation contribute insights for engineers, researchers, and industry professionals involved in the design, deployment, and optimization of multi-energy microgrids.

Grid-forming inverters are the essential components in the effort to integrate renewable energy resources into stand-alone power systems and microgrids. Performance of these inverters directly depends on their control parameters embodied in the controller. Even the most conscientiously designed controller will exhibit suboptimal performance upon implementation due to the presence of parasitic elements in the existing hardware. Hence, the controller has to be tuned and optimized. In the present article, the process of implementation, laboratory verification, and tuning of a matching-controlled grid-forming inverter is presented. In order to assess the efficiency of the grid-forming controller, its operation has been tested and analyzed in blackstart, steady state, and transient operation. For this purpose, a systematic sensitivity analysis has been conducted and the control parameters have been tuned in laboratory tests. The laboratory results verify proper operation of a 7 kW grid-forming inverter in all three test scenarios. After applying the proposed method on the tested grid-forming inverter in steady state operation, total harmonic distortion (THD) of the output voltage is less than 0.5% for its practical loading range (maximum THD is less than 1% in no-load condition). The system is able to blackstart and supply the loads. Finally, the studied grid-forming inverter is stable in the presence of severe step load changes and disturbances, i.e., voltage overshoot is managed well and compensated for with a low settling time using this approach.