Frame-angle-based controller for 3φ interconnected PV systems

Abstract

This paper presents the development and performance of a controller for photovoltaic (PV) systems that are grid-connected through a 3φ wavelet modulated (WM) dc-ac power electronic converter (PEC). The proposed controller is designed using decoupled current control loops, which have the d — q-axis components of the currents injected to the grid, as their inputs. The outputs of this controller are command values for the d — q-axis components of the voltages produced by a 3φ WM dc-ac PEC (v∗Id and v^∗Iq). The values of v∗Id and v∗Iq are used to determine the required angle ê, which aligns the frame spanned by the actual d-q-axis components of the voltages produced by the controlled 3φ WM dc-ac PEC (vId and vIq). The adjustments of ê allow changing the phase angles of the sinusoidal reference signals used to generate the wavelet modulation switching pulses. The proposed controller is implemented for performance testing using a 15 kW ac module PV system that is interconnected through a 3φ, 6-pulse, WM dc-ac PEC. The performance of the frame-angle controller is tested for different changes in the power delivered to the grid and system parameters. Test results demonstrate stable, fast, and accurate control actions that are complimented by negligible sensitivity to levels of power delivery to the grid, as well as variations in system parameters.