Robust Control of Load Voltage in an Islanded Wind Energy Conversion System Using Nonlinear Methods

Renewable wind energy is a significant source of green energy supply that has gained considerable attention and development in numerous countries in recent years. These systems are utilized as islanded units in circumstances where it is not feasible to establish a connection to the network. Various structures exist for these systems, but the focus of many studies has been on wind energy conversion systems based on a squirrel cage induction machine with back-to-back converters. When operating in islanded mode, this structure necessitates specific control requirements, with the most crucial being the supplying of the desired voltage and frequency of the load. In this paper, two control structures are proposed and constructed to regulate the load voltage by controlling the load-side converter. Two control loops have been implemented in the first control structure. The inner loop utilizes the state feedback input-output method to control the voltage, while the outer loop employs the sliding mode method to control the power components. The objective is to derive the control law for the reference biaxial voltage of the load-side converter. The second proposed structure incorporates the voltage controller sliding mode control method in the inner loop and then the state feedback input-output method is employed in the outer loop to control the current components of the load-side converter, thus designing the system control input. The simulation results of both structures in MATLAB software have been compared by introducing various disturbances to assess the control systems' resilience to each other and the common proportional-integral linear control structure. In the suggested method, voltage and current variations manifest concurrently in the control structure predicated on power components.