A Smart Control for Dual Mode Multi-Functional Grid Interface Single-Stage PVEG-BES System

This article presents a neutral current harmonic compensation strategy for a grid interface single-stage photovoltaic energy generation-battery energy storage system with a seamless transition feature. Unbalanced single-phase loads connected at the common point of the interconnection (CPI) draw a distorted grid current, causing third-order harmonic currents to flow from the utility main neutral line. In addition, this current causes excessive overheat of the neutral conductor. Owing to these issues, a modified reduced order generalised integrator (MROGI) based approach is presented for neutral line current harmonic compensation, grid current balancing, and power factor enhancement. Furthermore, the grid current distortion limit in the grid following mode is kept within the limits set by the IEEE std. 519 and 929, respectively. The auto-synchronising controller generates a control signal for the static transfer switch used for islanding/auto-resynchronisation using a frequency-locked loop based on MROGI, which is in coherence with the IEEE std. 1547. Grid-forming control is realised through a multi-loop proportional resonant-proportional control to maintain sinusoidal voltage across loads. The proposed power management scheme regulates the system power and protects the battery from overcharge/deepdischarge conditions. The performance of the control algorithm is verified using the developed prototype through OPAL-RT-5600 under different operating conditions.