MPPT Enabled LnC2n-2Impedance Network-Based Modular Multioutput Nonisolated Grid Connected Hybrid Converter With Reduced Leakage Current

Abstract

A parasitic capacitance (CPV) is formed between a large conductive photovoltaic (PV) panel and the ground, resulting in a strong leakage current causing power loss, electromagnetic interference (EMI), and safety concerns while feeding the ac loads or grid. Introducing a transformer eliminates leakage current between the PV system and grid, but it is costly and introduces losses. Additionally, there is a growing interest in multioutput hybrid converters (MOHCs) that cater to existing ac and emerging dc utilities. Furthermore, these MOHCs use the same set of switches for simultaneous dc and ac operations, compromising between the duty cycle (d) and modulation index (mi), where their sum does not exceed one. To address these challenges, this article proposes a maximum power point tracking (MPPT) enabled LnC2n-2 impedance-network based modular nonisolated grid-connected MOHC with reduced leakage current. The proposed MOHC is expandable with n stages, and at higher n, it achieves higher voltage gains at lower d, providing a broader operating range for mi. Thus, a standard voltage rating is achievable despite the constraint where the sum of d and mi does not exceed one. Furthermore, the proposed MOHC uses LnC2n-2 impedance network at the input side thus, it is free from EMI interference unlike the conventional voltage source inverter-based MOHC. To illustrate this concept, a prototype of a basic L2C2 impedance-network MOHC for n = 2 is developed, enabled with an incremental conductance MPPT algorithm, and connected to the grid was tested up to 960 W. The converter's performance is evaluated under steady-state, dynamic, MPPT, and grid-connected conditions. © 1982-2012 IEEE.