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Microgrids are designed to connect different types of AC and DC loads, which require robust power controllers to achieve an efficient power transfer. However, the effects of both AC and DC disturbances in the same type of controller make achieving stability a design challenge, especially in coupled systems where disturbances affect both the upstream and downstream in the microgrid. This paper presents an analysis of a second-order sliding-mode control (SOSMC) applied to a microgrid with direct-current (DC) and alternating-current (AC) power converters. The aim is to simulate the second-order sliding-mode control with buck converters that feed constant DC–DC and DC–AC power loads. The controller was tested in consideration of a unique sliding surface facing external disturbances, such as variations in the frequency of AC converters, sudden changes in upstream voltages, and constant power loads (CPL). The influence of the gain values (K) on the controller was also analyzed. The results show that the controller is robust regarding its sensitivity to external disturbances and steady-state error. However, the importance of the constant "K" in the model states that there exist K-limit values where if "K" is too low, a slowdown is presented, and the response against disturbances can be critical, and if is too high, an overshoot is presented in the output voltage. [ABSTRACT FROM AUTHOR]

This paper presents an experimental validation of a non-linear sliding-mode control based on a washout filter when is submitted to alterations in the load, control parameter, and voltage reference. The numerical and the experimental tests are compared to visualize the nonlinear effects caused by the power electronic converters and a comparison of the errors obtained for both test is presented. The results show that similar behaviors are presented in both cases with low error in the controlled variable vc. Furthermore, when representing bifurcations, both tests show similar behaviors, although the experimental test has a low displacement in the signal. This method is useful to monitor non-linear effects of micro grid and to design new filters or modify settings in the parameters. [ABSTRACT FROM AUTHOR]