Trinary Hybrid Cascaded H-Bridge Multilevel Inverter-Based Grid-Connected Solar Power Transfer System Supporting Critical Load

Abstract

Higher power rating solar photovoltaic systems are emerging in the power system owing to the reduction in the cost of photovoltaic arrays and environmental concerns of the conventional power generation systems. Multilevel inverters are reported at high power levels due to reduced switching frequency and increased efficiency. Cascaded H-bridge (CHB) multilevel inverters have been reported in the literature due to its redundant structure compared to other multilevel topologies. When CHBs with dc sources are in the ratio of 1:3, it is named as a trinary hybrid multilevel inverter, and it generates a maximum number of equal output voltage levels. In this article, a trinary CHB multilevel inverter-based grid-connected solar power transfer system using modified second-order generalized integral control is proposed. A two-stage solar PV system consists of a single-input-multiple-output single-ended primary inductance converter and two CHB structures per phase used to verify the proposed system. A modified second-order generalized integral control is presented for active power control and grid synchronization. The controller is designed to eliminate dc-offset from the sensed load currents and to ensure balanced, sinusoidal, and unity power factor grid currents. Moreover, the shunt-connected system mitigates the reactive power and harmonic demands of the local load, thus maintaining the grid current power quality within the standard prescribed by IEEE-519. The performance of the proposed system is validated with an experimental prototype, and the test results validate the theoretical claims.