## 1 Introduction  
Climate change brought on by environmental pollution has given rise to new requirements for energy conversion efficiency. Specifically, the transportation sector is one of the main contributors to pollution due to its reliance on internal combustion engines [1]. Currently, more efficient transportation technologies such as electric vehicles (EVs), hybrid vehicles (HVs), and hybrid electric vehicles (HEVs) are being explored. The first uses batteries (Bs) [2; 3], the second uses a combination of internal combustion and electrical power [3; 4], and the latter has an energy storage system that can be composed of ultracapacitors (UCs), batteries (Bs), and fuel cells [5; 6; 7]. EVs and HEVs today are considered a viable alternative since they offer an intelligent and efficient transport system without polluting emissions [8; 9; 10; 11; 12]. Companies such as Honda, BMW, Kia, and Tesla, among others, already offer electric vehicles powered by batteries for sale [1; 8; 13]. Recently some authors have studied the infrastructure and environmental impacts of EVs in different cities. These authors determined that the use of EVs is viable because electricity costs are much lower than the gasoline costs per km of the vehicle [10; 11; 12; 13]. However, this type of vehicle has the problem of having less autonomy than HVs and long charging times [14]. Therefore, there are currently HEV prototypes powered by batteries (Bs) and ultracapacitors (UCs) [7; 14; 15; 16], which feature good performance and autonomy [14; 16; 17; 18]. A hybrid energy storage system (composed of UCs and Bs) in an HEV can recover more energy, extend battery life, and increase the driving range unlike EVs [13; 14]. HEV energy consumption depends on the power rations of the components, the control strategy applied, the type of terrain, and the vehicle topology. Regarding the latter, there are few studies that explore different vehicle topologies or power configurations. These HEV powertrain topologies or configurations should be studied to analyze their influence on the performance of the vehicle from the analytical point of view [18]. Some typical configurations of the powertrain system include the basic passive parallel that does not contain power converters in its configuration and therefore no control is applied to meet the energy demand, unlike the ultracapacitor/battery (C-UC/B) configurations, battery/ultracapacitor (C-B/UC) configurations, and multiple converter (C-MC) configurations that have power converters [7; 16]. However, the C-UC/B and C-B/UC configurations only have a two-way direct current to direct current (DC/DC) power converter for either the Bs or the UC and a control is needed to meet the load demand. On the other hand, a feature of the multiple converter configuration is its two bidirectional DC/DC power converters connected in parallel with the power sources (UCs and Bs). This configuration leads to control over the two power converters to meet the load demand. Another feature is that the UC voltage can be varied over a wide range, which implies that the UC is used in full capacity; in addition, the voltages of both the B pack and the UC bank can be kept below the voltage of the DC bus [16]. In this context, this work analyzes and evaluates an HEV with an energy storage system composed of Bs and UCs with a Multiple Converter configuration (C-MC), for which no analytical results have been shown using an electric model. To analyze the proposed configuration, the following methodology is used: (i) the parameters of a vehicle, powertrain, and an energy management strategy are taken from the literature; (ii) the C-MC configuration is modeled electrically; (iii) the configuration is tested in CITY II and ECE driving cycles; and (iv) finally, the performance of the proposed configuration is compared with other topologies.