Energy-efficient cost-effective inverter configuration for residential photovoltaic systems

A parallel inverter configuration for residential photovoltaic (PV) systems consisting of two inverters of different sizes is proposed. The power rating for one inverter is small in order to handle the frequently occurring low-insolation conditions, while a larger inverter handles the high-irradiance, high-power regime. A control strategy optimizes the overall dc-ac conversion efficiency by ensuring that the two-inverter unit does not stray into the low-efficiency operating regimes associated with partial and excessive loading. Simulation results for 9 kW systems in Tennessee and Colorado show that implementing the suggested configuration can lead to average dc-ac conversion efficiency increases of up to 20% compared with using a single inverter. A detailed cost-benefit analysis is conducted to determine the economic feasibility of the suggested configuration. The analysis reveals that the suggested configuration would not be profitable under current residential electricity prices. However, increases in electricity prices and incentives for solar systems will make it a lucrative alternative to traditional systems in the future. Furthermore, the two-inverter unit introduces potential reliability improvements, which can eliminate the need for costly inverter replacements over the lifetime of the PV array, leading to additional significant economic benefits.