Energy-balance control of PV cascaded multilevel grid-connected inverters under level-shifted and phase-shifted PWMs

Abstract

This paper presents an energy-balance control strategy for a cascaded single-phase grid-connected H-bridge multilevel inverter linking n independent PV arrays to the grid. The control scheme is based on an energy-sampled data model of the PV system and enables the design of a voltage loop linear discrete controller for each array ensuring the stability of the system for the whole range of PV arrays operating conditions. The control design is adapted to Phase-Shifted and Level-Shifted Carrier PWM to share the control action among the cascadeconnected bridges in order to concurrently synthesize a multilevel waveform and to keep each of the PV arrays at its maximum power operating point. Experimental results carried out on a 7-level inverter are included to validate the proposed approach.