Interleaved high conversion ratio DC–DC converter with output self‐balancing and current auto‐sharing for DC nanogrid application

Abstract

In the application of bipolar DC bus configuration in the DC nanogrid, the unbalanced voltage of two outputs in bipolar DC bus, due to the unbalanced conditions of loads and/or energy sources, will cause deterioration of the power quality of the bus and may damage the switch, affecting the stability and safety of the system. In order to solve the problem of unbalanced voltage of two outputs, interleaved series capacitor based dual‐output converter with a high conversion ratio is presented in this paper. By applying negative current mode (NCM) to the main inductor, the character of two‐output self‐balancing and zero voltage switching (ZVS) of all switches for such this topology configuration is achieved. In the NCM mode, the parallel diodes of main switches are not conducted during dead time and guarantee the flowing path to load side. Thus, based on this condition, volt‐second balance of main inductor is obtained to get the character of two‐output self‐balancing. Furthermore, by adopting series capacitor in the proposed topology and based on the charge‐balance of the intermediate block capacitor, inductor current existed in the two phase could be auto‐sharing. Comprehensive operational principle analysis, loss analysis, and efficiency of the proposed converter under different load conditions have been given, and the comparison analysis of three operation modes and selection of negative current mode is clarified. Small signal model of the proposed converter is described to convenient for the controller design. Finally, simulation results and a 20–220 V prototype are built to verify the character analysis of the proposed converter.

Unified small‐signal model for DC‐DC converters based on the three‐state switching cell operating in discontinuous conduction mode

“…After that, it is necessary to differentiate the terms on both sides of the resulting expression with respect to time, also assuming that the derivatives of average values are null. Considering that the first-order derivatives of the variables with respect to time are denoted by "^" and after some manipulation, it is possible to write (29).…”

“…One can also analyze the stability of multi‐input and interleaved converters based on SSA as in Athikkal et al 27 and Kumar and Kumar, 28 respectively. As demonstrated in Chen et al, 29 the small‐signal modeling of a non‐isolated high step‐up interleaved converter involves the manipulation of high‐order matrices.…”

Modular DC‐DC converter with reduced current ripple and low voltage stress suitable for high voltage applications

“…To nail this purpose, more power switches are used with different voltage stresses 14–16 . The high gain coupled inductor (CI)‐based dc‐dc structures provide the turn ratio of windings as an additional degree of freedom alongside duty cycle of main switches 17–19 . However, it is necessary to apply a clamping circuit in order to eliminate the voltage spikes upon their power switches generated by the presence of their leakage inductances 20,21 .…”

“…[14][15][16] The high gain coupled inductor (CI)-based dcdc structures provide the turn ratio of windings as an additional degree of freedom alongside duty cycle of main switches. [17][18][19] However, it is necessary to apply a clamping circuit in order to eliminate the voltage spikes upon their power switches generated by the presence of their leakage inductances. 20,21 The voltage multiplier (VM) is the most commonly used technique to boost the output voltage, which can be categorized into two types: voltage multiplier cell (VMC) and voltage multiplier rectifier (VMR).…”