Double integral action based sliding mode controller design for the back-to-back converters in grid-connected hybrid wind-PV system

In this paper, a double integral sliding mode based nonlinear controller (DISMC) is developed for the grid-connected hybrid wind-PV system. The proposed control approach provides better steady state response and robustness as compared to the existing control methods. The topology considered in this study for the wind and PV based hybrid distributed generator system is efficient. Wind and PV generator are connected to the utility grid via boost converter at the machine side followed by inverter at the grid side. Thus, the realized scheme has reduced number of DC-DC conversion stages as compared to the previous schemes. So far, no study investigates the design of nonlinear controller for this scheme. Proposed DISMC offers the maximum power point tracking (MPPT) for both wind and PV generator, DC bus voltage regulation, and smooth transfer of active power to the utility grid. Firstly, the detailed small-signal mathematical models for the proposed hybrid system and DC bus dynamics are developed. After that, three control laws based on DISMC are designed to ensure the stable operation under varying weather conditions and system uncertainties. Then, the stability of the hybrid system is proved using Lyapunov theory. Finally, the performance of the proposed framework has been verified using model-based MATLAB time-domain simulations, and controller hardware-in-the-loop (C-HIL) experiments. The superiority of the proposed control technique was approved by comparing the result with other control methods.