This paper investigates the control problems of the single-phase grid connected to the photovoltaic system through an inverter with LCL filter. The control objectives are threefold: (i) forcing the voltage in the output of PV panel to track a reference signal provided by the MPPT block; (ii) regulating the DC link voltage to ensure the power transferring from the source to the grid; (iii) providing a current with sinusoidal waveform and in phase with the grid voltage by means of controlling DC/AC converter (PFC). Firstly, a simulation module based on the mathematical model of a PV panel is utilized to predict the maximum total power from PV array. Secondly, a nonlinear module based on the mathematical equations of the whole controlled system is developed. At last, a nonlinear multi-loop controller is synthesized using the sliding mode technique. The results are confirmed by simulations which show that the proposed regulator is robust with respect to changes of Climate factors.

This paper focuses on the problem of controlling a single-phase grid connected to the photovoltaic system with L filter. In this system the DC/AC converter is constituted by two stages: a boost power converter and a single phase inverter. The main control objective is threefold: (i) extracting maximum possible power from photovoltaic module MPPT (ii) tight regulation of the DC link voltage (iii) the power factor correction requirement must be satisfactorily realized. The proposed strategy combines two cascaded nonlinear proportional-integral controllers under pulse-width modulation feedback. The design methodology is developed by using the singular perturbation technique where two time-scale dynamics are artificially induced in the closed-loop system. The Filippov's average model is applied in order to reduce the DC/AC controller design to the continuous-time controller design. It is formally demonstrated, through theoretical analysis and simulation results in MATLAB/SIMULINK that the proposed design methodology achieves desired objectives and it validates the performance of controllers.

This work addresses the problem of controlling single-phase shunt active power filter (APF) in presence of nonlinear loads. The aim of control is twofold: (i) compensation of the current harmonics and the reactive power absorbed by the nonlinear load; (ii) guaranteeing a regulated DC bus voltage of the converter. The considered problem is dealt with using a singular perturbation approach that involves two loops in cascade. An inner-loop is designed, using the nonlinear proportional integral controller, to cope with the compensation issue and an outer-loop is designed to regulate the DC bus voltage of the converter. In this paper the nonlinear proportional integral controller is developed using the singular perturbation technique where two timescale motions are artificially induced in the closed-loop system. A detailed analysis of the stability control system is presented and the controller performances are illustrated by simulation in Matlab/Simulink environment.

This paper focuses on the problem of controlling single-phase shunt active power filters (APFs) operating in the presence of nonlinear and uncertain loads. The main difficulties when controlling this kind of filter are the existence of a strong non-linearity of the system and state variables inaccessible to measurements. This paper proposes a double-loop cascade controller developed on the basis of the singular perturbation technique in order to meet two main control objectives: (i) the inner-loop is designed to compensate the harmonic and reactive currents absorbed by the nonlinear load enforcing power factor correction; (ii) the outer-loop is synthesized to regulate the inverter output capacitor voltage. The controller also includes two-time scale sliding mode observer to estimate the network voltage that is not accessible to measurement. In this work, the singular perturbation technique and averaging theory are used for a complete and rigorous formal analysis to describe the control system performances. The effectiveness of this approach has been successfully verified through computer simulations using the Matlab/Simulink environment.