A step-by-step full-order sliding mode controller design for standalone inverter-interfaced cleaner renewable energy sources

Power electronic inverters are one of the most significant components for the integration of clean energy systems and the proper control of these power electronic interfaces helps to enhance power quality. This paper presents a robust step-by-step full-order sliding mode voltage control strategy for standalone single-phase inverters that can be interfaced with cleaner renewable energy sources. The proposed controller employs a cascaded method through outer- and inner-loops to facilitate tracking of the desired load voltage. In contrast to the most commonly used sliding mode techniques for interfacing these cleaner energy sources, which usually utilize the canonical-form of the system's state-space model, the designed controller uses a block-controllable model that mitigates unwanted noises. To design the controller, the capacitor voltage and the inductor current of the LC filter are measured to be employed in the outer second-order sliding mode voltage control loop and the inner first-order sliding mode current control loop, respectively. The utilization of such full-order sliding surfaces in each step effectively reduces the chattering in the control signals as well as facilitates the transient and steady-state responses with less harmonic distortion and thereby, promoting the effective integration of renewable energy sources. To verify the performance of the proposed controller under various loading conditions as external disturbances, a 2.2 kW standalone single-phase inverter is simulated using MATLAB/Simulink platform along with a microcontroller-based processor-in-loop through the digital signal processing. In terms of internal disturbances, the proposed controller is also tested under different filter parameters’ variations over a wider range. The results indicate a better alignment for coupling with clean energy sources and the comparisons with other control techniques show better performance of the proposed controller.