A detailed design and optimization process of a stand-alone photovoltaic AC transformer-less regulated three-phase voltage generator

This paper deals with a synthetic design process, in a Matlab/Simulink environment, of an overall photovoltaic energy conversion system, consisting of a stand-alone, (50Hz, 3×380 V), transformer-less electrical power supply (3KWp). Starting from the basic schematic of an off-grid PV system, the first step is dedicated to the identification of each stage main external electrical characteristics, in order to build up a homogenous conversion chain, responding to the fixed objective. This is done without ignoring many of the practical sizing constraints to make the final design as near as possible to its detailed field realizable configuration. A progressive modelling process is then initiated with the chosen structure of the PV array (PVG). As a result, the external characteristics of the latter are established in presence of the main field perturbations such as solar irradiance intensity, temperature and shading variations. A maximum power point tracking stage (MPPT), based on the “perturb & observe” (P&O) approach as a control strategy of a boost DC-DC converter is then introduced, implemented and optimised. Its behaviour is investigated under a multitude of the various working conditions quoted above, along with the load constraints. At this level, these are related to the battery pack mainly arranged to fulfil DC bus voltage considerations. Significant results in this scope are presented, before introducing a three-phase Voltage Source Inverter (VSI), which direct control circuits are based on the analog PWM technique. An output voltage regulation loop is then designed to assure optimum static and dynamic performances in presence of the main user AC load perturbation profiles. At the end, significant and realistic operating conditions are introduced to evaluate the overall performances of the completed installation, before conducting some representative validating tests which related results are presented and discussed.