A hybrid two‐stage modular DC–DC converter with zero‐voltage switching

Abstract

Conventional modular multilevel converters (MMCs) are widely used in high power applications due to their various astonishing advantages; however, they fail to achieve balanced capacitor voltage in DC operation. In this paper, a hybrid two-stage modular DC-DC converter is proposed to solve the issue of unbalanced capacitor voltages. The proposed converter consists of a singlephase half-bridge MMC with half-bridge submodules followed by a medium voltage valves-based H-bridge rectifier. The proposed converter is used in medium-voltage applications such as feeding a DC-load or interconnection between two DC grids of different voltage levels. The proposed configuration achieves successful DC-DC conversion with a low number of switches, a high conversion ratio with bidirectional power flow, low current stresses, soft switching across the second stage, and low switching losses. The operational concept and the control algorithm have been illustrated in detail. Finally, the effectiveness of the proposed DC-DC converter is evaluated based on simulation studies of MATLAB SIMULINK and a scaled-down laboratory experimental test rig.

A hybrid half‐bridge submodule‐based DC–DC modular multilevel converter with a single bidirectional high‐voltage valve

“…In addition, the employed HV valves increase the converter losses due to their relatively high conduction and switching losses. In [29], the aforementioned arm current reversal approach has been employed, but the second stage half-bridge SMs (4 arms) are replaced by series-connected switches-based HV valves (4 valves). The valves are operated under zero-voltage switches to reduce the converter switching losses, that is, enhance the converter efficiency.…”

Coordinate control strategy for two‐stage wide gain DC/DC converter

“…1 The use scenarios of two-stage cascade power converter are increasing, and it has been widely used in new energy fields such as photovoltaic (PV) system, electric vehicle charging, and DC microgrid. [2][3][4] In the two-stage converter system, a large, heavy, and expensive DC bus capacitor is used to link the front and rear converters to filter the output voltage of the front converter, so that the rear converter can obtain a stable DC input. At the same time, it absorbs all current ripple of each converter connected to it and balances the instantaneous power difference of the two-stage converter.…”

“…With the development and wide application of new energy technology, single‐stage power converter has gradually failed to meet the requirements of new energy system for wide gain and high efficiency 1 . The use scenarios of two‐stage cascade power converter are increasing, and it has been widely used in new energy fields such as photovoltaic (PV) system, electric vehicle charging, and DC microgrid 2–4 . In the two‐stage converter system, a large, heavy, and expensive DC bus capacitor is used to link the front and rear converters to filter the output voltage of the front converter, so that the rear converter can obtain a stable DC input.…”

Real time online efficiency optimization of buck converter against variable voltage and load change

“…Another way to reduce switching loss is to employ PWM soft switching technology, particularly the primary-side phase shifted (PPS) full-bridge (FB) DC-DC converter, which is extensively used. [12][13][14][15][16][17][18] It adopts the phase shift control approach to produce soft switching by leveraging the circuit's inherent resonance settings, reducing the switching loss to a minimum. It is extensively adopted in applications like vehicle chargers due to its continuous frequency-based duty cycle adjustment, but because it is challenging to produce ZVS at a light load, the converter's efficiency is significantly reduced in this situation.…”

“…However, these converters have significant voltage and current stresses in the switches and considerable circulating losses. Another way to reduce switching loss is to employ PWM soft switching technology, particularly the primary‐side phase shifted (PPS) full‐bridge (FB) DC‐DC converter, which is extensively used 12–18 . It adopts the phase shift control approach to produce soft switching by leveraging the circuit's inherent resonance settings, reducing the switching loss to a minimum.…”