# Independent Double-Boost Interleaved Converter with Three-Level Output
## 1 Introduction  
The need for high-gain boost topology converters with a low ripple of the input current can be justified in various applications, such as bidirectional chargers for electric vehicles in smart homes [1], development of energy storage for renewable power systems [2; 3; 4], and DC microgrid and mobility-related concepts [5; 6; 7; 8]. The present work focuses on the power conversion stage of low voltage DC renewable sources, such as photovoltaic panels with power optimizers and/or micro-inverter applications in AC or DC distribution microgrids [9]. The classic interleaved boost converter is recognized for its high efficiency and low ripple input current. On the other hand, this type of converter exhibits a limited voltage gain. High-gain interleaved DC-DC voltage converters in transformerless structures have been explored in various studies [10; 11; 12; 13]. A floating, high-gain voltage interleaved converter widely employed in research studies was analyzed in [14; 15]. This structure is based on the principle of the intercalated operation of two classic boost converters. However, the output circuit for this application does not have purely capacitive filtering, thus it requires a more complex scheme for the output voltage control. Numerous studies commonly use the three-level boost converter [16], but since the input source and inductor currents are the same, there is no interleaved characteristic, and the voltage gain is limited. The same limitations were found in the research of [17], where a three-level DC-DC boost converter with dual output was presented. An interleaved step-up DC-DC converter topology composed of two boost converters was introduced in [18]. During operation, the converter stages are indirectly connected in a series, which ensures a high voltage gain of the output. Since the output consists of two series capacitors, a three-level output is achieved. The individual voltage drop across each capacitor is balanced according to the operating state of the converter, but a fully independent control is not achieved forthis approach, and the efficiency at a low input voltage is limited. The same limitation regarding the independent voltage balancing of the output capacitors was found in [19]. High voltage gain non-isolated converters without coupled inductors exhibit a simpler structure, being more suited for low power level applications [20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31]. In Ref. [20], high conversion gain and efficiency were achieved using an interleaved topology. To acquire high voltage gain with low voltage stress across the semiconductor devices, [21] proposed the usage of an active-passive inductor cell configuration for a step-up DC-DC converter, and [22] showed that the implementation of a switched capacitor topology allowed a wide voltage gain range. In Refs. [23; 24; 25; 26], multistage diode-capacitor (MSDC) networks were implemented. Similarly, in Ref. [27], a switched inductor and switched capacitor multilevel topology was involved, with the output voltage distributed among multiple levels of output capacitors, subsequently reducing the voltage stress on the components. Using two duty ratios to operate the switched states of the converter, Ref. [28] attained high voltage gain without using extreme values of these duty ratios, thus the voltage conversion proved to be more efficient. In addition, in Refs. [29; 20; 31], the converter topologies employed an interleaved design, with the inductors switched in a parallel and series configuration during the charging and discharging states. Despite the high voltage gain, in all the variants mentioned above, there was high voltage stress across the power semiconductors. All these converter topologies have good gain and efficiency, and some also have interleaved properties, but none have a three-level output with fully controlled voltage operation.