Peak Current Control and Feed-Forward Compensation for the DAB Converter

This paper presents a double band peak current control for the DAB converter that permits to avoid the risk of transformer saturation. Additionally, feed-forward compensation is employed to achieve a fast transient response under load variations. The proposal is described, analyzed, and numerically simulated

Solid State Transformer with Integrated Input Stage

In this paper, a solid state transformer (SST) with integrated stages is addressed. The SST has been originally proposed for traction applications, after as an option to face the new requirements of the distributed generation but also suggested in many applications. There are different topologies, from one to three stages; certainly each one with their advantages and limitations. Some challenges for this type of systems are reducing the cost and increasing the efficiency.The components reduction is discussed in this paper, by integrating two stages of the SST; the ac/dc converter and the DAB converter share one leg. The proposed scheme is described and numerically simulated

Volume Optimization in Si IGBT based Dual-Active-Bridge Converters

Dual-Active-Bridge (DAB) converters are able to step up/down DC voltage in a wide range by adopting medium frequency transformer (MFT) for isolating and converting voltage level. Increase in switching frequency of Si IGBTs reduces the MFT size instead it intensifies the semiconductor switching losses which leads to increase in the heatsink size. In this paper variation of heatsink volume versus frequency is compared versus MFT. MFT and heatsink volume of a 5 kW 600 to 400 V DAB converter are optimized. Obtained results show that variation of switching frequency in range 1-10 kHz increases the size of optimal heatsink by 3 times, i.e V HS,opt ∞ √(fs [kHz])

dv/dt filter design incorporating machine impedance and voltage slew rate for WBG-based electric drives

The trend towards high power density and high reliability of electric drive systems in mobility applications pushes the use of high-speed machine in combination with Wide Band Gap (WBG) power semiconductor technology. Replacement of Si power technology with WBG without mitigating high voltage slew rates dv/dt degrades machine winding insulation. Of the different mitigation techniques employed, especially the passive LCR filter at the output of the inverter cannot be optimally designed without consideration of the inherent low impedance of the high speed machines. This paper presents the analytical techniques used for LCR filter design for motor drives and introduces the technique to incorporate machine impedance Z dm for optimal design of the parameters to achieve high efficiency. An analytical technique based optimization algorithm is introduced for the reduction of filter inductor volume to achieve high power density in these applications. The proposed design methodology is evaluated in simulations and experiments with Gallium Nitride (GaN) based inverter technology

Double Active Bridge Operated in Quasi Discontinuous Conduction Mode

The quasi discontinuous conduction mode (QDCM) of the double active bridge (DAB) is addressed in this paper. The DAB converter usually is operated turning on always two semiconductors per bridge, and this leads to a continuous inductor current: However, a similar operation to dc/dc converters can be implemented, for this, less than two switches are turned on, at certain time, in one of the bridges; this leads to the quasi-DCM. With this mode of operation, a natural soft-switching is performed during the whole range of operation, but also low current stress is performed compared to the square modulation, not only at low power range. The modulation is relatively simple compared to other techniques. The proposed technique is described, analyzed, numerically simulated, and experimentally tested

Theoretical Evaluation of Semiconductor Loss Components Behavior in ISOP-DAB Converters

Input-Series Output-Parallel (ISOP) connected Dual-Active-Bridges (DABs) form an interesting topology which enable step down MVDC to LVDC by employing medium frequency transformers. Si-IGBT semiconductor devices are commonly used in power distribution grid applications such as Smart Transformers (STs) where both MVDC and LVDC energy ports can be presented. In this paper, Si-IGBT semiconductor loss components such as conduction, switching and gate driver losses behavior are theoretically evaluated in a wide range of blocking voltage, switching frequency and phase-shift angle of DAB converters. In addition, gate driver losses are approximated as a continuous function of blocking voltage based on available datasheets. The behavior of the loss components are analyzed for two 50 and 500 kW ISOP-DAB converters where DC voltage ratio is 10 kV/400V

Impact of Grid Forming Power Converters on the Provision of Grid Services through VSC-HVdc Systems

High Voltage dc (HVdc) transmission systems have gained increased popularity as a flexible and efficient power transmission option with higher grid controllability. Widespread adoption of HVdc systems for interconnecting power systems and integrating large renewable energy generation facilities such as wind farms, has forced the power system to undergo a transition from a predominantly ac system into a hybrid ac-dc system, especially in the high voltage transmission grid. This paper attempts to provide an overview on the role of Voltage Source Converter based HVdc(VSC-HVdc) systems within the evolving power system as a grid services provider. Special attention is paid to discuss the impact of Grid Forming converter control approach on the provision of such services through VSC-HVdc systems