Research Keyword: Power Converters

Aug 22

Design and Implementation of 1 MHz DC-DC LLC Resonant Converter with GaN Enhancement Mode HEMT

In this paper, a 1 MHz LLC half bridge resonant converter with GaN Enhancement mode HEMT (GaN E-HEMT) is implemented. The power density of the power converter is improved with higher switching frequency and achieve higher efficiency with soft switching technique. The operating principle of half bridge LLC resonant converter is discussed and the characteristics and gate driver circuit requirements of the wide bandgap devices are studied. Finally, the digital signal processor, TMS320F28035, is used to realize the laboratory prototype with the input voltage 400 V, the output voltage 12 V, and rated output power 240W. The synchronous rectifier is used on the secondary side to reduce conduction loss to improve efficiency. The experimental results show that efficiency can be as high as 94.1% at 50% load and 92.1% at full load.

Aug 22

Design and Implementation of 3.5 kW Digital Controlled Battery Charge System

A 3.5 kW digital controlled battery charger is implemented with the ripple feed forward (RFF) technique to reduce the output voltage ripple. This battery charger is composed of front-stage of interleaved boost converter for PFC and full-bridge resonant converter for DC-DC conversion. The full load conversion efficiency of the full-bridge resonant converter is 94.3%, and the highest efficiency of system is 93.9%. Mostly, the output voltage ripple is reduced about 30 % by using the RFF.

Aug 21

Hybrid Sorting Strategy for Modular Multilevel Converters With Partially Integrated Second Life Battery Energy Storage Systems for fast EV charging

Electric vehicles charging stations requires huge amounts of power from the grid, what can be alleviated with battery energy storage systems. Two-Level converter is the preferred topology for commercial BESS, but this topology do not offer modularity for the energy storage stage. This work proposes a parallelized Modular Multilevel Converter with partially rated storage systems with an overall control scheme that governs independently the active power reference of each BESS-SMs. The proposed control allows the operation with any amount of Dummy-SMs, which are SMs with floating capacitors in their DC-link without battery energy storage unit. This feature allows the converter to keep operating under batteries faults or disconnection, facilitating the integration of 2nd life batteries to BESS-SMs with different degradation levels. The intra-power balance and the control of the capacitors voltage of Dummy-SMs, is achieved through an hybrid sorting of carriers made in the modulation stage, where LS-PMW is used. This hybrid control strategy, allows the converter to operate each of its SMs as BESS or Dummy, depending of the connection or disconnection of its BESS.

Aug 21

Computationally Efficient Predictive Control of Photovoltaic Central NPC Inverter with Constant Switching Frequency

This paper proposes a computationally efficient modulated model predictive current control method for a three-phase neutral point clamped (NPC) central inverter in the photovoltaic energy system. The proposed control method calculates the optimal sector number based on grid voltages, grid currents and maximum power point tracking and uses a subset of voltage vectors to reduce the number of calculations significantly. The subset of voltage vectors are used to predict the future behavior of grid currents and DC-link capacitor voltages. A triangular-region based cost function chooses four optimal voltage vectors for seven-segment switching method. The proposed control method provides low steady-state errors, fast transient response and a constant switching frequency. A 817-kW photovoltaic energy system is simulated to validate the proposed control method.

Aug 21

A Dual-Active Single-Ended Wireless V2H System with Self-Synchronized Phase-Difference Control Method

This paper discusses the bidirectional Wireless Power Transfer (WPT) device for vehicle-to-house (V2H). It makes use of a simple, compact single-ended converter and a phase-difference control mechanism that is self-synchronized. This paper proposes a way whereby phase difference control could well be self-contained just on the slave side without mutual communication. This method allows for high-power wireless transmission despite the low coupling coefficient between the transfer coils. The phase difference and transmission power can be altered by changing the MOSFET conduction time on one side without synchronizing the phases on both sides.

Aug 20

Modulated Predictive Current Control with Reduced Computational Burden for Back-to-Back NPC Converter in PMSG Wind Energy System

This paper proposes a novel modulated predictive current control with a reduced computational burden for a three-phase back-to-back connected neutral-point clamped (NPC) converter in permanent magnet synchronous generator (PMSG) based wind energy system. An algorithm has been developed to determine the optimal sector number based on measured generator- and grid-side voltages and currents. The eight voltage sectors in the optimal sector are then used to determine optimal triangular region (among 6) that produces the minimum cost function value for NPC rectifier and inverter. The three voltage vectors in the optimal triangular region are
selected and applied to the rectifier and inverter via seven segment switching scheme. The dwell times of medium voltage vectors in the switching sequence are adjusted dynamically to balance the DC capacitor voltages. The proposed approach produces constant switching frequency, minimal steady-state errors and fast transient response. The developed control scheme is tested on a 3 MW, 3000 V PMSG wind energy system through MATLAB simulations.

Aug 19

Design and Implementation of an SiC-based 48 V-380 V Dual Active Bridge DC-DC Converter for Batteries Employed in Green Hydrogen Microgrids

-A 48 V-380 V DC-DC dual active bridge converter is designed and implemented for a DC microgrid employed in a hydrogen production system.
-The bidirectional converter can be useful to supply the 380 V DC busbar interfaced with a 48 V battery
-The converter can be also utilized as a unidirectional power converter to supply the 48 V electrolyser
-Technical guidelines on designing the converter for the hydrogen production system are developed

Aug 17

AC/DC Converter Topologies Comparison for More Electric Aircraft Application

This paper describes the potential AC/DC power converter topologies that are appropriate for medium voltage and medium/high power aircraft applications. The power converter’s rated power and the DC distribution voltage level are 1MW and 3kV. The solutions explore multiple and modular converter structures that are connected in series and/or in parallel to achieve the rated power and DC-link voltage. The main aim of this research is reviewing the resulting AC/DC converters topologies and then the best candidate for the target application. The loss and efficiency of the converter topologies are determined based on available SiC semiconductor devices. Simulation results obtained using PLECs software to compare between different power converter topologies in terms of loss, converter weight, and power density to identify the best candidate.

Aug 16

A Novel High Step-up Voltage Gain DC-DC Converter with Low Source Current Ripple

A novel high gain DC-DC converter based on two phase interleaved inductors and switched capacitor
networks is proposed.
The proposed converter has following advantages over other existing converters.
(i) High step-up voltage gain over complete duty cycle range(0 to 1),
(ii) Equal current sharing among the two inductors over the complete duty cycle range which helps in
reducing number of current sensors as explained in the paper
(iii) Reduced ripple in the low voltage side DC source which is good for sources such as battery or
photovoltaic cell or fuel cell and
(iii) Reduced voltage stress on the power switches, diodes and capacitors.
The mathematical proof of above claims with comparative results are given .
The simulation as well as experimental verification results are given in this paper.
The systems such as electric vehicles , grid interphase of energy storage systems and solar systems,
hydrogen cell applications require high step-up gain DC DC converters and this research addresses most
of the problems related to this converter.

Aug 07

A Secondary-Side Resonant LLC converter for Reducing Resonance Voltage with Boost Mode Operation Using Resonance Including Current Doubler Rectifier

Isolated DC-DC converters in data centers are now required to have a high step-down ratio and be suitable for high-power applications. As such DC-DC converters, LLC resonant converters have been attracting attention. However, the LLC resonant converter generates a large resonance voltage at the resonator, so the resonance inductor and resonance capacitor must be large in size. Recently, a previous study proposed a secondary-side resonance LLC converter to reduce the resonant voltages of the passive components. Nevertheless, this LLC converter requires a resonant capacitor in parallel with the rectifier to achieve boost mode operation, which complicates the circuit operation and design. Therefore, we have considered the use of the magnetizing inductance of the coupled inductor of the current doubler rectifier as a method to realize the boost mode operation. In this paper, we propose a new method of boost mode operation for LLC resonant converter using secondary-side resonance and the current doubler rectifier.