Design of an On-Grid Microinverter Control Technique for Managing Active and Reactive Power in a Microgrid

Abstract

This paper presents the design and implementation of an on-grid microinverter control technique for managing active and reactive power based on a dq transformation. The system was implemented in a solar microinverter development kit (Texas Instruments—TMDSSOLARUINVKIT). This microinverter has two stages: DC-DC and DC-AC. The DC-DC stage contains an active clamp flyback converter, where the maximum power point tracking (MPPT) of the solar panel is obtained with a current-based incremental conductance algorithm. The DC-AC stage comprises a dual-buck inverter in which voltage-, current-, and phase-tracking control loops are implemented to control the active and reactive power. These techniques were simulated in MATLAB using the proposed mathematical model and experimentally validated in the solar development kit. The results show that the simulated model behaved similarly to the real system, and the control techniques presented good performance. The maximum power point (MPP) of the solar panel was monitored in the DC-DC stage using a current reference provided by the incremental conductance MPPT algorithm and was regulated by a 2P2Z control. The algorithm is robust against continuous changes in irradiance, as it quickly follows the ideal power and continually operates at a point close to the MPP. In addition, the active and reactive power control in the DC-AC stage enables the microinverter to supply the maximum active power. Moreover, the microinverter supplies reactive power according to a defined reference and within the established limits. The proposed mathematical model of the microinverter can be used to design new control techniques and other microinverter topologies. In addition, this active and reactive power-control technique can be implemented in low-power and low-cost microinverters to successfully maintain power quality in small microgrids.