A Vector-controlled Single-phase Voltage Source Inverter Based Grid Interface Suitable for Variable Frequency Operation in Autonomous Microgrids

Abstract

Vector (dq) control is a powerful technique used in high dynamic performance inverters. The transformation of AC into DC quantities allows one to get zero steady-state error for AC currents and voltages with simple proportional integrator type controllers. It can easily be implemented for three-phase inverters but presents some challenges for single-phase ones. The orthogonal component (β) required for the stationary to rotating frame transformation is usually created by phase shifting the real one (α) by one-quarter of a line cycle, which deteriorates the dynamic response. The emulation of a fictive orthogonal circuit for obtaining the β current component has been shown to yield enhanced transient response. This article shows that the dynamic response of vector-controlled single-phase inverters implemented with orthogonal circuit emulation is identical to that of a three-phase inverter. This concept is then extended for operation with variable grid frequencies, a condition that can be found in photovoltaic hybrid autonomous microgrids, where the grid frequency is used for energy management purposes. The effectiveness of this technique is demonstrated by means of simulation and experimental results.

Keywords:

• vector control
• current control
• inverter
• stationary frame
• rotating frame