# A New SEPIC-Based DC-DC Converter with Coupled Inductors Suitable for High Step-Up Applications
## 1 Introduction  
The European Union (EU) expects greenhouse gas emissions to be eliminated by 2050 and 100% replaced by renewable energy sources [1, 2, 3]. Solar energy is considered to be the largest source of energy [3]. In this context, solar energy technologies have experienced an increase in research to offer better efficiency at a lower cost. In order to achieve these goals, power electronics also deals with the conversion and storage of solar energy, the development of algorithms and control methods, etc. DC-dc converters play an important role in the conversion systems of photovoltaic panels (PV). In the literature, several solutions are proposed depending on the type of conversion that is required [4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60]. If the output voltage is required to be higher than the input voltage, a step-up converter needs to be used. The classical Boost topology is the simplest step-up converter with the lowest number of components [13]. One disadvantage of this converter is that if the required output voltage is much higher than the input voltage, this type of conversion cannot be achieved because of the intrinsic non-ideal components losses. However, on the market, different solutions, beginning with non-isolated high step-up dc-dc converters like: cascaded converters [14, 15, 16, 17], semiquadratic converters [18], quadratic converters [19, 20, 21], stacked step-up converters [22, 23], hybrid converters [24, 25, 26, 27], multi-input converters [28], multiphase converters [17, 29] and ending with isolated step-up topologies [30] have been reported. If a step-down converter is required, one of the solutions could be the traditional Buck converter [13]. If an extremely low conversion ratio is required, it cannot be obtained with the classical Buck converter, but different converters have been proposed in theliterature, such as cascaded [31; 32], quadratic [33], multiphase [34] or hybrid step-down converters [24; 25; 26; 27], etc. In this paper, a new SEPIC-based step-down/step-up converter is presented, and it is compared to other types of step-down/step-up topologies. Similar to the classical Buck and Boost converters, the Buck-Boost converter has the advantage of having the lowest number of components among the step-down/step-up topologies [13]. The disadvantage of this converter is the control, which is difficult because the transistor is floating, and the output voltage polarity is opposite to that of the input voltage. In the literature, different Buck-Boost-type topologies can be found, beginning with a buck-boost converter with positive output voltage, presented in [35], a bidirectional buck-boost converter [36; 37; 38], cascaded [39], quadratic [40] or multi-input converters [41; 42], etc. Also, the classical Cuk, SEPIC and ZETA converters [13; 61] are of step-up/step-down nature. The classical transformerless SEPIC converter has the advantage that the output voltage has the same polarity as the input voltage [13]. The authors in [24; 25; 26; 27] are using a switched capacitor or switched inductor structure that it is inserted into the traditional SEPIC topology for increasing the step-up or step-down capabilities. In reference [43], it is shown that a quadratic SEPIC converter can be used in microgrid applications to obtain a high-voltage gain at a low-duty cycle and it exhibits a continuous input current, like in the classical transformerless SEPIC. Another structure with a reduced input current ripple and higher step-up capabilities is presented in [44]. In [45; 46; 47; 48; 49; 50], different structures of nonisolated SEPIC converters with some examples of design, analysis and control are presented. In [61], the classical SEPIC with isolation is presented, analyzed, and implemented.