Abstract
The control of the current injected into the grid with lower harmonics is considered as one of the most important issues for the grid integration of distributed energy resources (DERs). The unbalances and harmonics in the grid voltage usually pollute the current injected into the grid due to the power electronic interfaces, for example, inverters. To address such problems, the present paper proposes a nonlinear higher order sliding mode controller (HOSMC) for grid-connected three-phase inverters with LCL $\mathrm{LCL}$ filters in order to control the current injected into grid and improve the power quality. The proposed current controller injects the desired current into the grid with lower values of total harmonic distortions (THDs) under any grid voltage condition as well as it reduces the harmonics in the grid voltage. Apart from these, the proposed scheme is developed to provide robustness against parametric uncertainties where these uncertainties are modeled using the Taylor series expansion method. Finally, the performance of the system is evaluated using processor-in-loop (PIL) simulations via MATLAB/Simulink platform through the implementation on a system considering the capacity of the DER as 2 kVA per phase and compared with other existing control strategies.
Highlights
Power electronic interfaces with different types of filters are considered as integral parts for connecting renewable energybased distributed energy resources (DERs) with the main power grid [1, 2]
This paper focuses to design a higher order sliding mode controller (HOSMC) for three-phase grid-connected inverters with LCL filters in order to effectively facilitate the integration of DERs
A robust nonlinear current controller is designed for gridconnected three-phase inverter-interfaced distributed generators using the higher-order concept of the sliding mode control strategy
Summary
Power electronic interfaces with different types of filters are considered as integral parts for connecting renewable energybased distributed energy resources (DERs) with the main power grid [1, 2]. In [18], two robust SMCs are designed based on super-twisting algorithms for L- and LC- filtered single-phase inverters in islanded/anti-islanded operation modes with considering parametric uncertainties in which the presented algorithms are robust against disturbances, using loworder filters reduces the attenuation gain as long as the effects of harmonics are not eliminated carefully as the low-order sliding surfaces are used. In light of literature so far presented in this paper, the main problems (excluding the chattering phenomenon) with existing SMCs for single- or three-phase grid-connected in inverters are the robustness against parametric uncertainties, distortion in the grid voltage, THDs in the grid current, and unbalances in the grid voltage. This paper focuses to design a HOSMC for three-phase grid-connected inverters with LCL filters in order to effectively facilitate the integration of DERs. The robustness of SMCs against parametric uncertainties depends on the modeling of these uncertainties. Highlighting the main finding of this work along with comments on future works
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