Single‐stage AC module with series power decoupling capability for connecting PV to a single‐phase power grid

Abstract

In single-phase grid-connected photovoltaic inverters, the input power is constant during the grid period, whereas the output power oscillates at double-line frequency. Therefore, electrolytic capacitors are widely used to handle the input and output power differences. However, these capacitors have short lifetime which degrade the inverter reliability. This paper proposes a control strategy to turn a conventional four-switch flyback-based inverter to an inverter equipped with a series power decoupling circuit. Therefore, a long lifetime film capacitor can be used as the main energy storage. The modified inverter has an inherent snubber circuit, which can restore energy of the transformer leakage inductance and improves its overall efficiency. The control strategy can realise maximum power point tracking and inject a sinusoidal low total harmonic distortion current to the grid. A 100 W prototype inverter has been built to verify operation and feasibility of the proposed control strategy.

Investigation of single‐stage transformerless buck–boost microinverters

“…High gain single‐stage inverter topology based on coupled inductor is presented in few literature [37, 60]. The core drawback of such configurations is the harmful effects of leakage inductance [15, 61]. Leakage inductance effect has been nullified in the topology shown in Fig.…”

Enhanced soft‐switching strategy for flyback‐based microinverter in PV power systems

“…The energy stored in the magnetising inductance is transferred to the grid through the secondary switch. The resonant and magnetising current is given as (18) and (19), where the resonant frequency…”

“…The application of electrolytic capacitors for decoupling has been reported to constrain the inverter's lifespan. A number of solutions have widely been reported in the past with a cost of reducing the converter efficiency [17][18][19]. New capacitor technology has been gradually developed to replace the conventional aluminium electrolytic counterparts for high efficiency and long lifetime.…”

Microinverter Topology based Single-stage Grid-connected Photovoltaic System: A Review

“…A challenge of two-stage microinverter is dealing with power interface when DC power from the solar module is transferred to the AC-grid side. By referring to Figure 2a, there is a capacitor called as DC link, which connected in parallel between first and second-stage in order to balance out the power difference [11] performance [21].…”