Comparative Analysis of Single and Double-Stage Grid-Tied PV Systems

This paper presents a comparative study of the single-stage and double-stage configurations of single-phase grid-connected solar PV systems based on efficiency, power quality, cost-effectiveness, stability, and control complexity using Simulink. Boost converter exclusively takes care of maximum power point tracking (MPPT), and inverter converts DC into AC in double-stage topology while in single-stage, both the jobs are done by inverter itself. The single-stage topology has the advantage of cost-saving and slightly higher overall efficiency at the cost of bigger DC bus capacitor while in double-stage topology, the DC bus voltage is maintained almost constant by boost converter and hence capacitor of lesser value is required. The problem with single-stage configuration is that the DC bus oscillations (which are also panel voltage oscillations), reduces the average power drawn from the PV panel, resulting in poor MPPT efficiency. The LCL filter keeps the total harmonic distortion (THD) in the injected grid current within limits. The second-order generalized integrator (SOGI) is used for orthogonal signal generation for synchronous reference frame-phase locked loop (SRF-PLL). The Inc. algorithm is used for MPP tracking. The control of inverter is done by using the synchronous reference frame so the PI controller can be used to track the DC quantities and to get intercycle dynamics along with independent control of active and reactive powers.