A Rapidly Reconfigurable DC Battery for Increasing Flexibility and Efficiency of Electric Vehicle Drive Trains

Abstract

This paper proposes a drive train topology with a dynamically reconfigurable dc battery, which breaks hard-wired batteries into smaller subunits. It can rapidly control the output voltage and even contribute to voltage shaping of the inverter. Based upon the rapid development of low-voltage transistors and modular circuit topologies in the recent years, the proposed technology uses recent 48 V power electronics to achieve higher-voltage output and reduce losses in electric vehicle (EV) drive trains. The fast switching capability and low loss of low-voltage field effect transistors (FET) allow sharing the modulation with the main drive inverter. As such, the slower insulated-gate bipolar transistors (IGBT) of the inverter can operate at ideal duty cycle and aggressively reduced switching, while the adaptive dc battery provides an adjustable voltage and all common-mode contributions at the dc link with lower loss. Up to 2 /3 of the switching of the main inverter is avoided. At high drive speeds and thus large modulation indices, the proposed converter halves the total loss compared to using the inverter alone; at lower speeds and thus smaller modulation indices, the advantage is even more prominent because of the dynamically lowered dc-link voltage. Furthermore, it can substantially reduce the distortion, particularly at lower modulation indices, e.g., down to 1 /2 compared to conventional space-vector modulation and even 1 /3 for discontinuous pulse-width modulation with hardwired battery. Other benefits include alleviated insulation stress for motor windings, active battery balancing, and eliminating the vulnerability of large hard-wired battery packs to weak cells. We demonstrate the proposed motor drive on a 3-kW setup with eight battery modules.

Hierarchical State-of-Charge Balancing and Second-Harmonic Current Suppressing Control With a Scalable DC Reconfigurable Battery Pack

“…The duty cycle balancing methods have better performance compared to conventional energy redistribution balancing methods [8]. A variety of reconfigurable topologies have been proposed [1], which can be divided into ac RBPs [10], [11], and dc RBPs [12], [13] by the output voltage. The typical dc RBP equips each cell with a half-bridge circuit, which is the most widely studied and applied due to its low complexity [14]- [16].…”

Simulation and Testing of Self-Reconfigurable Battery Advanced Functions for Automotive Application

“…As shown in many articles [1], battery-switching technologies of Self-Reconfigurable Batteries (SRBs) promise significant improvements in terms of autonomy and battery life, cell balancing [2][3][4][5][6][7], recharging capacity [8][9][10][11], improving the efficiency of vehicle drive trains [12][13][14] and even cell aging [15][16][17]. Their operating principle is as follows: switches are added to the power paths linking the cells to enable the number of active stages in series and parallel to be modulated dynamically [18], depending on the type of SRB.…”

Hybrid Nearest-Level Switching Modulation for a Wide Output Bandwidth at Low Switching Frequency and High Output Quality

“…On the one hand, a higher output bandwidth allows higher signals and/or a wider spurious-free spectral range to reduce losses and degradation of materials as well as bearings [17], [18]. On the other hand, switching slower for the same maximum output frequency would allow the use of transistors, particularly insulated-gate bipolar transistors (IGBT), with lower conduction loss at the price of higher switching loss [19], [20]. Outside the conventional grid and drives applications, the requirements can differ greatly.…”