Output current observation and control of grid-connected modular multilevel converter using a simplified super twisting algorithm sliding mode

• The proposed observer allows accurate current observation in grid-connected MMCs by using an SSTA-SM Luenberger Observer (SSTA-SMLO), eliminating the need for a physical current sensor and thereby reducing system costs. • The proposed SSTA-SMC demonstrated marked improvements in output current quality under steady-state and dynamic conditions compared to a traditional PI method, particularly during variations in power reference and grid voltage. • The SSTA-SM strategy excels in achieving finite-time convergence and high robustness, making it a reliable control technique for grid-connected converters under different operating conditions. This paper presents a method for observing and controlling the output current of a grid-connected Modular Multilevel Converter (MMC) using a Simplified Super Twisting Algorithm-Sliding Mode (SSTA-SM). This strategy effectively observes and controls the output current under steady-state and dynamic conditions. For the current observation, a Simplified Super Twisting Algorithm-Sliding Mode Luenberger Observer (SSTA-SMLO) is employed. This observer combines the simplicity of the Luenberger Observer (LO) with the robustness of the SSTA-SMO, providing high estimation accuracy while reducing system complexity. Moreover, the proposed Simplified Super Twisting Algorithm-Sliding Mode Control (SSTA-SMC) strategy ensures excellent control performance while maintaining the important features of traditional Sliding Mode Control (SMC). A MATLAB-based simulation and comparative analysis were conducted, evaluating SSTA-SMLO and SSTA-SMC against a Sliding Mode Observer (SMO) and a conventional proportional-integral (PI) controller. The results demonstrate that SSTA-SMC and SSTA-SMLO surpass the classic methods.