Abstract
This paper proposes a cascade control structure for three-phase grid-connected Photovoltaic (PV) systems. The PV system consists of a PV Generator, DC/DC converter, a DC link, a DC/AC fully controlled inverter, and the main grid. For the control process, a new control strategy using nonlinear Backstepping technique is developed. This strategy comprises three targets, namely, DC/DC converter control; tight control of the DC link voltage; and delivering the desired output power to the active grid with unity power factor (PF). Moreover, the control process relies mainly on the formulation of stability based on Lyapunov functions. Maximizing the energy reproduced from a solar power generation system is investigated as well by using the Perturb and Observe (P&O) algorithm. The Energetic Macroscopic Representation (EMR) and its reverse Maximum Control Structure (MCS) are used to provide, respectively, an instantaneous average model and a cascade control structure. The robust proposed control strategy adapts well to the cascade control technique. Simulations have been conducted using Matlab/Simulink software in order to illustrate the validity and robustness of the proposed technique under different operating conditions, namely, abrupt changing weather condition, sudden parametric variations, and voltage dips, and when facing measurement uncertainties. The problem of controlling the grid-connected PV system is addressed and dealt by using the nonlinear Backstepping control.
Highlights
Solar Photovoltaic (PV) energy is a potential and environmentally friendly resource of energy which has become widely explored till date owing to its omnipresence, availability, free gas emission, and reduced maintenance cost
Adopting a Maximum Power Point Tracking (MPPT) technique is imperative as there is a probable mismatch between the Maximum Power Points (MPP) of the PV module and the load characteristics
The performances of the designed nonlinear controller will be evaluated by simulation on a three-phase low-voltage grid-connected PV system under different operating scenarios
Summary
Solar Photovoltaic (PV) energy is a potential and environmentally friendly resource of energy which has become widely explored till date owing to its omnipresence, availability, free gas emission, and reduced maintenance cost. Because of the nonlinearity of the PV power systems and the unpredictable intrinsic and atmospheric changes, the operating point is always varying due to the control unit (DC/DC converter and/or inverter). A considerable progress has been made over last decade in optimization techniques in order to perform the threefold objectives Among these methods, classical PID controller is usually used in industry and literature because of its robustness, low cost, and ease of implementation. This paper proposes a Backstepping based technique to design a suitable control system for the grid-connected PV system. The designed control technique ensures the optimal energy transfer to the grid via sharing active and reactive power into the grid regardless of the atmospheric changes and parametric uncertainties.
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