Grid Interconnection of Renewable Energy Sources at the Distribution Level With Power-Quality Improvement Features

TLDR

Renewable energy resources are increasingly connected to distribution systems via power electronic converters. The paper proposes a novel control strategy to maximize benefits of grid‑interfacing inverters in 3‑phase 4‑wire distribution systems. The inverter is controlled as a multi‑function device that can act as a power converter and a shunt active power filter to compensate current unbalance, harmonics, reactive power, and neutral current, either separately or together. Simulations and laboratory experiments show that the control makes the inverter‑load combination appear as a balanced linear load to the grid.

Abstract

Renewable energy resources (RES) are being increasingly connected in distribution systems utilizing power electronic converters. This paper presents a novel control strategy for achieving maximum benefits from these grid-interfacing inverters when installed in 3-phase 4-wire distribution systems. The inverter is controlled to perform as a multi-function device by incorporating active power filter functionality. The inverter can thus be utilized as: 1) power converter to inject power generated from RES to the grid, and 2) shunt APF to compensate current unbalance, load current harmonics, load reactive power demand and load neutral current. All of these functions may be accomplished either individually or simultaneously. With such a control, the combination of grid-interfacing inverter and the 3-phase 4-wire linear/non-linear unbalanced load at point of common coupling appears as balanced linear load to the grid. This new control concept is demonstrated with extensive MATLAB/Simulink simulation studies and validated through digital signal processor-based laboratory experimental results.