An Improved Control Strategy for Single-Phase Single-Stage Grid-Tied PV System Based on Incremental Conductance MPPT, Modified PQ Theory, and Hysteresis Current Control

Abstract

In this paper, a modified variable step Incremental Conductance (VS-InCond) algorithm integrated with modified pq theory and double-band hysteresis current control (PQ-DBHCC) is proposed for the implementation on a single-stage single-phase grid-tied photovoltaic (PV) inverter system. As the single-phase inverter in a grid-tied PV system receives varying DC voltage from PV modules, the PQ-DBHCC strategy is deployed to regulate the ac output voltage along with its capability to deliver the maximum power during onload conditions. VS-InCond algorithm and DC-link capacitor are used as the interface between the PV modules and the inverter for tracking maximum power point. Furthermore, the PQ-DBHCC strategy also controls active and reactive power between inverter, load, and grid. The simulation results obtained from MATLAB Simulink software show that PQ-DBHCC strategy is capable of achieving the desired fixed DC voltage at inverter input and maintaining the maximum power point tracking, even under varying environmental conditions and load variations. The inverter ac output has a steady 230 Vrms at 50 Hz frequency. The total harmonic distortions (THDs) of output ac current and ac voltage are observed to be less than 5%, as recommended in IEEE 519 standard. Additionally, during full load conditions, the proposed system successfully delivers 95% of the theoretical maximum power from PV modules.