RMS voltage control with harmonic compensation for parallel-connected inverters feeding non-linear loads

Droop method is an advantageous technique for generating the grid in stand-alone AC supply systems with distributed generation. Regarding the AC voltage regulation, an interesting approach is to control the RMS voltage instead of its instantaneous value. However, this regulation has serious drawbacks when feeding non-linear loads since the voltage THD increases and current harmonics are not equally shared by the inverters. This paper proposes a harmonic compensation which reduces the voltage THD and makes that the current harmonics are equally distributed among the inverters. Simulation results demonstrate the improvements of the proposed control.

I. Introduction

In case of remote locations with difficult access to the electric grid, a stand-alone system is more economical. As a matter of fact, these systems are broadly introduced in hilly regions and remote villages and applied for many applications such as rural electrification, auxiliary power units for emergency services or military applications, and manufacturing facilities using delicate electronics [1].