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This study presents a single-phase grid-tied photovoltaic (PV) system based on a global maximum power point tracking (MPPT) technique, which is performed by means of the particle swarm optimisation (PSO) method. The PSObased MPPT technique is employed to solve problems related to mismatching phenomena, such as partial shading, in which the PV arrays are commonly submitted. Considering the search of the global maximum power point under partial shading, the effectiveness of the PSO-based MPPT technique is highlighted when compared with the wellknown perturb and observe MPPT technique, since both the mentioned MPPT techniques are used to determine the dcbus voltage reference to ensure a proper grid-tied inverter operation. A current generator algorithm based on a synchronous reference frame is proposed, which operates in conjunction with a dc-bus controller and MPPT algorithms, computing the reference current of the grid-tied inverter. In addition, the current generator controls the energy processed by the PV system to avoid over power rating of the grid-tied inverter, since the active power injection into the grid, reactive power compensation and harmonic currents suppression are carried out simultaneously. The performance and feasibility of the grid-tied PV system are evaluated by means of simulation and experimental results.

This study proposes a phase-locked loop (PLL) algorithm employed for phase-angle detection of single-phase utility grid voltage. A detailed stability analysis is performed, as well as its performance is evaluated under several power quality problems. The proposed PLL structure is based on the instantaneous active power theory for three-phase power systems (pPLL), which is investigated into the fictitious two-phase stationary reference frame (αβ-pPLL). A non-autonomous adaptive filter (AF) operates in conjunction with the PLL, and its main function is to extract the fundamental component of the utility grid voltage allowing the rejection of voltage harmonics. The stability analysis of the proposed AF-αβ-pPLL scheme is carried out in order to provide adequate tuning procedures for choosing the parameters used in the proposed algorithm. In addition, the dynamic response and robustness of the AF-αβ-pPLL algorithm are evaluated by means of simulation and experimental tests, under utility grid disturbances, such as voltage harmonics, voltage sag, phase jumps and frequency variations. To emphasise the effectiveness of the algorithm, a comparative analysis with three other single-phase PLL schemes is carried out, such as the conventional power-based PLL (pPLL), the two-phase stationary reference frame pPLL (αβ-pPLL) and the well-known enhanced PLL (EPLL).

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