Faster Convergence Controller With Distorted Grid Conditions for Photovoltaic Grid Following Inverter System

Abstract

The hysteresis current controller (HCC) for grid following inverter (GFI) system with $LCL$ -filter is a well-known controller for its robustness, fast reference tracking, better dynamics, and easier implementation compared to other controllers. However, HCC behaves differently while integrating such a system with solar photovoltaics (PV). The PV-based GFI system requires fast convergence while transferring maximum power from PV to the grid at minimum converter losses through GFI. This paper therefore proposes a modified double-band HCC (MDBHCC) with proportional resonant (PR) controller for single-phase PV integrated GFI system with LCL-filter. The proposed algorithm implements a unipolar symmetrical PWM strategy for reducing inverter switching losses through a sequential logic with an adaptive clock. It improves the variation in switching frequency and limits the maximum switching frequency of HCC while enhancing the total harmonic distortion (THD) of the injected current into the grid at the point of common coupling. To alleviate the power quality problem and achieve zero steady state error, the proposed MDBHCC with PR control operates at lesser % THD. Simulation and experimental results are presented, with a significant decrease in switching frequency and an improvement in grid current harmonics at both steady-state and dynamic conditions.

Keywords

• GFI
• hysteresis current control
• LCL filter
• power quality improvement
• total harmonic distortion