A composite power decoupling method for a PV inverter with optimized energy buffer

A composite passive and active power decoupling method is proposed and optimized for a photovoltaic (PV) inverter. The proposed composite power decoupling (CPD) method has the following merits: 1) the dc side passive power decoupling (DC-PPD) can be automatically activated/deactivated according to the solar power to maintain more than 99% maximum power point tracking efficiency and low total harmonic current distortion (THDi); 2) the film capacitor with high reliability can be used due to the optimization of the energy buffer, e.g., a reduction of 52% and 23% in capacitance (or buffer energy) compared to DC-PPD and ac side active power decoupling, respectively; 3) control scheme developed in the d-q frame has more simple structure and requires less measurements than the existing methods. The experimental results show that the proposed CPD can dynamically control the dc-link voltage ripple under various conditions such as the abrupt change of the solar power and the load. Besides, low dc-link voltage ripple and low THDi are achieved in both steady-state and transient periods. Particularly when the solar power is less than 74%, the proposed CPD (with 261 μ F) has better performance than the traditional used PPD (with 1120 μ F). This article is accompanied by a video demonstrating the parameters optimization and measured waveforms.