Title : Feasible Performance Evaluations of Digitally-Controlled Auxiliary Resonant Commutation Snubber-Assisted Three Phase Vo

† Corresponding Author: beiranvand@modares.ac. ir Tel: +98-2182884344, Tarbiat Modares University Faculty of Electrical and Computer Engineering, Tarbiat Modares University, Tehran, Iran International Journal of Industrial Electronics, Control and Optimization . © 2021 IECO. efficiency, and low electromagnetic interference (EMI). Owing to the aforementioned advantages, the PSFB dc-dc converter is widely used in battery chargers [6-10]. Generally, the dissimilarity between internal resistance, capacity, self-discharge rate, and the environment temperature result in voltage imbalances in series-connected lithium-ion cells[1]. These voltage imbalances are progressively increasing during the discharging/charging intervals. Therefore, some cells may be over-discharged/charged even when the battery pack voltage is withing the safe boundries[10-13]. Consequently, the battery pack capacity is reduced and sometimes an explosion may occur. Thus, for the sake of the batteries and assuring safety, some equalization strategies are crucial to eliminate the voltage imbalances. Due to the aforesaid reasons, battery equalizing has become an important part of the BMS[1]. The equalization topologies are roughly classified into two groups: dissipative and non-dissipative methods [1]. In the dissipative method, the extra energy of over-charged cells is dissipated across some resistors or Zener diodes which decrease the efficiency, and cell capacity but, the equalization speed is relatively high. Besides, there is a considerable number of switches, and gate drivers in the equalizing circuit. Therefore, this method suffers from high cost, and control complexity. In contrast to the previous method, in the non-dissipative method, the additional energy in the over-charged cells is exchanged between cells or between cells and battery pack. As a result, higher efficiency and reliability are achieved. Based on the energy flow direction, the non-dissipative method consists of six major groups including adjacent cell to cell (AC2C), direct cell to cell (DC2C), any cell to any cell (AC2AC), cell to pack (C2P), pack to cell (P2C), and cell to pack to cell (C2P2C). In the AC2C method, the additional energy is transferred between two adjacent cells which may reduce the equalization speed. Moreover, the number of switches and inductors are proportionally increased by increasing the number of series-connected cells. Therefore, this method suffers from control complexity and bulky size [13-17]. In [13] a modified buck-boost converter is used across the two adjacent cells and, the equalization path is controlled by turning the power MOSFETs on and off. [14] proposes a Cuk converter with a fuzzy logic control system, where operation of the employed Cuk converter is similar to the buck-boost converter. In the switched-capacitor converters (SCCs), one switched-capacitor unit is implemented across every two adjacent cells [15]. By switching the complementary MOSFETs across two adjacent cells, the extra energy is transferred between these cells. In the DC2C method, the extra energy can be transferred between different cells in different positions. Consequently, the number of switches is more than twice of the number of cells which results in more control complexity, and larger size [18-21]. In [18] by utilizing a shared multi-secondary windings transformer, energy transportation can be obtained by forming buck-boost and flyback converters. In [19] four power MOSFETs and four diodes connected across each battery. By switching these MOSFETs, the charge transport can be provided for batteries in different paths. [20] proposes an ESS by using an LC resonant tank, where four MOSFETs have been connected across each batter. By turning these switches on and off and operating near the resonant frequency, the DC2C charge equalization is obtained. The additional energy can be exchanged simultaneously among all cells in all positions in the AC2AC method. Although the equalization speed is higher as compared to the AC2C and the DC2C methods, numerous switches, relays, and gate drivers are required [1, 22]. Thus, this method has some drawbacks; high cost, voluminous size, and control complexity, for instance. [1] uses a combination of a boost converter with an LC resonant converter for the voltage equalization. The boost converter is used to regulate the output voltage and the ZCS operation is obtained via the LC resonant converter. By switching the MOSFETs and relays, the equalization paths are obtained in different positions . Operation principle of the given converters in [1] and [22] are the same. In the C2P method, the extra energy is displaced from the over-charged cells to the battery pack [23-27]. A considerable number of switches and transformers are the main drawbacks of this method. Consequently, low efficiency and low modularity are obtained. In [25] the batteries are connected with each other through the multi-secondary windings transformer. The extra energy in batteries is stored in the magnetic core and by switching the MOSFETs it is transferred to the low voltage batteries. Similar to [25] in [26-27], the extra energy is stored in the magnetic core. But, these equalizers employ the flyback converter with one secondary winding transformer. Owing to the transferring energy between the high voltage and low voltage cells by a transformer, the C2P2C method is more efficient and faster than the C2P method [28-31], but it still suffers from a sizeable number of switches and multi windings transformers. The equalization system in [29] is based on a bidirectional flyback dc-dc converter and, therefore, the energy can be transferred either from one battery to another battery or from the pack to the batteries. Also the equalization system in [30-31] consists of two bidirectional dc-dc converters. In [30] the batteries voltages are sensed by one monitoring IC. But, in the [31] this action is done by using a transformer with multi-secondary windings. In these both topologies, the energy is transferred either from one cell to another cell or from the pack to the cells via magnetic cores. In the P2C method, the battery pack provides the required energy for low voltage cells. This method encompasses the full-bridge dc-dc converter [32], multi secondary windings transformer [33], and the VM. The VM based P2C method is also called as integrated converter International Journal of Industrial Electronics, Control and Optimization . © 2021 IECO. [13-15, 34-35]. In [32] the required energy for batteries with low voltages can be achieved from the pack voltage by sensing the batteries voltages and switching the MOSFETs. When one battery has a low voltage value, its bridge MOSFETs are turned-on to get its required energy from the other batteries. In contrast to all of the aforementioned methods, the equalization systems or both charging and equalization sections are integrated into a single system in the integrated method without increasing the number of switches or magnetic components. This feature leads to a simple, small, and competitive. But, all of the previously proposed integrated converters are only applied for low power applications and they have low efficiencies, too. This paper proposes a high power self-equalized battery charger by using the PSFB dc-dc converter with a voltage multiplier. By utilizing the proposed converter, both power and control circuits are significantly simplified. Due to the lack of power switches, sensors, and bulky magnetic components in the equalization circuit, both complexity, and