Abstract
In this paper, a module-level photovoltaic (PV) architecture in parallel configuration is introduced for maximum power extraction, under partial shading (PS) conditions. For the first time, a non-regulated switched capacitor (SC) nX converter is a used at the PV-side conversion stage, whose purpose is just to multiply the PV voltage by a fixed ratio and accordingly reduce the input current. All the control functions, including the maximum power point tracking, are transferred to the grid-side inverter. The voltage-multiplied PV modules (VMPVs) are connected in parallel to a common DC-bus, which offers expandability to the system and eliminates the PS issues of a typical string architecture. The advantage of the proposed approach is that the PV-side converter is relieved of bulky capacitors, filters, controllers and voltage/current sensors, allowing for a more compact and efficient conversion stage, compared to conventional per-module systems, such as microinverters. The proposed configuration was initially simulated in a 5 kW residential PV system and compared against conventional PV arrangements. For the experimental validation, a 10X Gallium Nitride (GaN) converter prototype was developed with a flat conversion efficiency of 96.3% throughout the power range. This is particularly advantageous, given the power production variability of PV generators. Subsequently, the VMPV architecture was tested on a two-module 500 WP prototype, exhibiting an excellent power extraction efficiency of over 99.7% under PS conditions and minimal DC-bus voltage variation of 3%, leading to a higher total system efficiency compared to most state-of-the-art configurations.
Highlights
Low-power residential rooftop and façade photovoltaic (PV) systems are expected to dominate in future distributed energy resources (DERs) and smart grid applications [1]
WP prototype, exhibiting an excellent power extraction efficiency of over 99.7% under partial shading (PS) conditions and minimal DC-bus voltage variation of 3%, leading to a higher total system efficiency compared to most state-of-the-art configurations
The most effective hardware solution for PS loss mitigation relies on module-level power electronics (MLPEs), which aim to maximize the power yield of each individual panel through dedicated maximum power point tracking (MPPT)
Summary
Low-power residential rooftop and façade photovoltaic (PV) systems (in the range of a few kW) are expected to dominate in future distributed energy resources (DERs) and smart grid applications [1]. The most effective hardware solution for PS loss mitigation relies on module-level power electronics (MLPEs), which aim to maximize the power yield of each individual panel through dedicated MPPT In this field, micro-inverter topologies have proven commercially successful, since they offer the flexibility to connect any number of PV modules directly to the AC grid [16]. Converter topologies with a large voltage boost ratio have been proposed for the interface between the low-voltage PV module and the high-voltage DC-bus, including cascade boost [23], coupled inductors [25], switching capacitors [26] and combinations of the above [27,28,29] These topologies are known to require complicated control algorithms [15] and, most importantly, employ electrolytic capacitors and magnetic components that limit the power density and the lifetime of the system, as found in [16,17]. The operating principles of the novel PV architecture are explained in Section 2, followed by operating simulationprinciples results on of a 5the kWnovel grid-connected residential
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