I. Introduction
Recently, there is a good attention on renewable energy sources and consequently the power electronic based systems to utilize these energy sources [1]. The renewable energy sources depend on the environment conditions and their characteristics are variables [2]. To provide a stable dc voltage, it is necessary to use different types of dc renewable sources simultaneously. For these applications, the multi-port dc/dc converters are the best solution to utilize the different types of dc voltage sources [2]. The multi-port dc/dc converters are divided into three main groups. These are single-input multi-output (SIMO), multi-input single-output (MISO), and multi-input multi-output (MIMO). Generally, these converters have simple topology, central control, high reliability and low construction cost [3]. In order to obtain a the safe and flexible electrical system with high reliability, it is necessary to use of renewable energy sources and or the combination of them with fuel cell and other energy storage elements. In this hybrid energy system (multi-input single-output converters) to combine input energy sources with different electrical characteristics and generate desired output levels are used [2]–[3]. Using renewable energy sources in the multilevel inverters lead to generate converters that consist of low power switches with minimum equivalent series resistance. These converters are able to connect to the power grid without using any transformers. Moreover, it is impossible to connect the high voltage dc-link of the multilevel inverters to the low dc voltage levels of renewable energy sources; in addition, the multilevel inverters needs balance voltage level for dc-link in order to have suitable performance. However, it is important to note that the diode-clamped multilevel inverter does not have the capability to balance dc-link voltage [4]. Moreover, there are some limitations to use of high voltage elements in the high voltage applications of the conventional dc-dc converters. As a result, the single-input multi-output converter has received more attention in the applications in which photovoltaic systems or fuel cell with multilevel inverter that need different controlled voltage levels are used.