PROPOSAL, ANALYSIS AND EXPERIMENTAL VERIFICATION OF NONISOLATED DC-DC CONVERTERS CONCEIVED FROM AN ACTIVE SWITCHED-CAPACITOR COMMUTATION CELL Mauricio Dalla Vecchia1, Jéssika Melo de Andrade2, Neilor Colombo Dal Pont2, André Luís Kirsten2 Proposal, Analysis and Experimental Verifi cation of Nonisolated 2DC-DC Converters Telles Brunelli Lazzarin Conceived from an Active1 EnergyVille, Switched-Capacitor KU Leuven, Commutation Kasteelpark Arenberg Cell 10, Heverlee, Belgium Mauricio Dalla2 Department Vecchia, of Jéssika Electrical Melo Engineering, de Andrade, Federal Neilor University Colombo of Santa Dal Catarina, Pont, Florianopolis André - SC, Brazil Luís Kirsten,e-mail: m.dallavecchia90@ Telles Brunelli Lazzaringmail.com; [email protected]; [email protected]; [email protected] [email protected] Abstract – This paper introduces a new family of impedance source circuit [3], [17], [18], series and parallel nonisolated dc-dc converters that are generated by the connections [19], [20], ladder [12], [14] and stacked integration of the active switched-capacitor (ASCC) and connection [21]–[23] have provided alternative ways to the conventional commutation cell (CCC). Based on the obtain high gain, but all of them use a higher number of commutation cell concept, the new conceived hybrid components. active commutation cell (HACC) provides three different The switched capacitor (SC) principle is one way to types of hybrid converters: buck, boost and buck-boost. multiply or divide dc voltage. The SC converters are applied All three converters are investigated in this study in boost topologies [10], [24], [25] as well as in buck through the following approaches: topological stages, topologies [26]. They are capable of supplying a high static gain analysis considering the switched - capacitor conversion ratio and they are magneticless topologies. features, generalization of the HACC and gain for M cells Almost all the structures have good voltage stress sharing and steady-state analysis. The buck version presents a across components and, when they are properly designed, high conversion rate, which demonstrates that it has they can provide high efficiency, high power density and low potential for step-down applications. To verify the weight [27]. However, the output voltage regulation is not as proposed topologies, a prototype was built with the easy as in a conventional converter and this represents a following specifications: 600 V input voltage, 150 V challenge in the design of SC converters. Many authors have output voltage, 70 kHz switching frequency and 1 kW addressed this issue in the literature [10], [26]. rated power. Efficiency close to 95% was obtained at On the other hand, the conventional converters present 1 kW for the buck topology, which demonstrates that the good output voltage regulation, but are not capable of proposed HACC can provide gain and high efficiency at providing a high conversion ratio. Hence, the integration the same time. between SC and conventional circuits could allow the combination of the advantages of the two groups of Keywords – Active Switched-Capacitor Cell, converters while overcoming the drawbacks [7], [11], [26]. Commutation Cell Concept, Experimental Results. This new family of converters is referred to in the literature as hybrid converters. I. INTRODUCTION In general, SC cells are integrated with conventional converters to generate new topologies [7], [11], [28]-[30]. The recent growth in the development and use of HVDC However, this concept was approached in relation to transmission systems, DC distributed systems, DC smart commutation cell, and a passive ladder SC cell was grids, electrical vehicles, energy storage systems, renewable integrated with conventional commutation cell [11]. The new sources, and telecommunication systems has enhanced the converters are analyzed through the commutation cell. need for new solutions for dc-dc conversion. This scenario In this context, this paper proposes a hybrid active brings new applications for dc-dc converters and challenges commutation cell (HACC) generated through the integration associated with managing the energy flow in these systems. of the active switched-capacitor cell (ASCC) and the More specifically, the current challenge in relation to dc- conventional commutation cell (CCC). The proposed cell dc conversion is to offer a high conversion ratio without generate three hybrid converters of different types: hybrid isolation, for step-up or step-down applications. The isolated buck, hybrid boost and hybrid buck-boost. These structures converters use the transformer turns ratio value to provide present modified static gain in relation to [11] and the gain. However, the transformer is a bulky component and conventional converters. Hence, they have advantages that when a high gain is required the intrinsic parameters become can be used in certain applications and thus, they can expand significant and this offsets its benefits [1], [2]. Recently, the range of applications of hybrid converters. A preliminary topologies based on switched-inductor [3]–[8], switched- study just about buck topology was presented in [31], in capacitor [3], [6]–[14], coupled inductor [3], [15], [16], which the topology was approached without considering the commutation cell principle. Manuscript received 24/04/2019; first revision 29/06/2019; accepted for The paper is divided as follows: firstly, the way in which publication 05/09/2019, by recommendation of Editor Marcello Mezaroba. the ASCC was integrated with the CCC is described and the http://dx.doi.org/10.18618/REP.2019.4.0031 Eletrôn. Potên., Joinville, v. 24, n. 4, p. 403-412, out./dez. 2019 403 new converters generated by this combination are presented. Subsequently, a theoretical analysis of the hybrid buck A similar approach was proposed in [11], where a hybrid topology is shown, addressing the main characteristics of the commutation cell was derived from a passive switched- topology. Finally, experimental results are presented to capacitor cell (implemented only with diodes). The two validate the proposed topologies. commutation cells are similar, with the ladder configuration and the same number of semiconductors, however, the II. INTEGRATION OF AN ACTIVE SWITCH proposed HACC uses three active and one passive switch CAPACITOR CELL WITH THE CONVENTIONAL while the commutation cell in [11] employs one active and DC-DC CELL three passive switches. Additionally, the converters generated by the integration of an active and a passive cells The conventional dc-dc cell (see Figure 1.a) is employed present different static gains, different topological stages and to generate the buck, boost and buck-boost classical are suitable for different applications, as will be presented converters. The ladder SC cell is used to provide step-up or and discussed in greater detail in Section III and IV. step-down circuits, where the gain can be increased by One of the advantages of SC circuits is that more SC cells adding more cells in a ladder connection [32]. This („M‟ cells) can be used to increase the conversion rate, as implementation can use passive (diodes) or active shown in Figure 3. This figure present the generalized hybrid (MOSFET, IGBT, SIC, GAN) switches. The cell proposed dc-dc buck converter, which can provide a high step-down herein is generated connecting the CCC (Figure 1.a) and the gain. The generalized boost and buck-boost topologies can ASCC (Figure 1.b) in a ladder configuration. To generate the be also obtained, following the input and output connections shown in Table I. The ladder configuration has the advantage proposed HACC (Figure 1.c), the terminals n1 and c1 of the that the voltage stress on the power components are equally CCC are connected, respectively, with the terminals b2 and a2 of the ASCC, as shown in Figures 1.a, 1.b and 1.c. The divided and clamped by the switched capacitors, thus when more SC cells are added the gain will increase but the HACC employs three switches (S1, S2 and S3), one diode voltage stress will remain constant. (D1), three capacitors (C1, C2 and C3) and one inductor (L). The resultant cell has three terminals, labelled „a‟, „b‟ and „c‟, in which the input dc-dc source and the output load are TABLE I connected. Connections Used to Generate the Three Proposed Conventional Active Switched dc-dc Converters Hybrid DC-DC Cell DC-DC Cell Capacitor Cell Terminals connected c Converter c1 Input Output c2 S 1 H-buck ca ba S S C 1 1 H-boost bc ac L n2 S n1 b1 2 C C1 C3 H-buck-boost cb ba S2 S3 L C3 D1 C2 b a2 D1 c a1 b2 a (a) (b) (c) S1 VIN Fig. 1. (a) Conventional dc-dc cell (CCC); (b) active switched- C M+1 1 capacitor cell (ASCC), and; (c) hybrid dc-dc cell (HACC). S2 C3 The topologies derived from the HACC have the input and cell 1 output connections described in Table I. With these connections, a family of three new nonisolated dc-dc Sy-2 converters is generated, as is shown in Figures 2.a, 2.b and VIN VIN Cx-2 M+1 2.c. The topologies are named as follows: hybrid dc-dc buck Sy-1 converter (Figure 2.a), hybrid dc-dc boost converter Cx cell „M‟ (Figure 2.b) and hybrid dc-dc buck-boost converter Sy L b VIN Cx-1 (Figure 2.c). It should be highlighted that the names buck, M+1 boost and buck-boost are used in relation to the connections D1 Co Ro Vo between input and output stages and do not necessarily a reflect the gain characteristics of the structures. Fig. 3. Generalization of the switched-capacitor cell for the c c c proposed hybrid dc-dc buck converter. S1 S1 S1 C1 C1 C1 VIN VIN S2 S2 S2 C Vo C III. THEORETICAL ANALYSIS OF THE BUCK VIN 3 3 C3 S3 L S L S3 L TOPOLOGY b 3 b b C2 C2 C2 D D D 1 Vo 1 1 Vo This section presents the theoretical analysis for the buck a a a converter (Figure 2.a), which is then extended to the boost (a) (b) (c) Fig.