Ravisekhar Nadimpalli Raju

10 kV/120 A SiC DMOSFET half H-bridge power modules for 1 MVA solid state power substation

In this paper, the extension of SiC power technology to higher voltage 10 kV/10 A SiC DMOSFETs and SiC JBS diodes is discussed. A new 10 kV/120 A SiC power module using these 10 kV SiC devices is also described which enables a compact 13.8 kV to 465/√3 solid state power substation (SSPS) rated at 1 MVA.

Advances in Power Conversion and Drives for Shipboard Systems

This paper presents some of the key advances in power electronics pertaining to shipboard electric power system applications. The focus is on the emerging wide bandgap semiconductor devices, i.e., silicon carbide (SiC) and gallium nitride (GaN) devices, and their potential impact on future shipboard power conversion and drives. Their benefits on power converter efficiency and power density are explained through a case study of a medium-voltage (MV) class motor drive system. SiC and GaN also enable new applications, including solid-state transformers, while posing new design and application challenges such as gate drive, protection, and interaction with loads. In addition to device related topics, this paper also overviews other important advances in power electronics, including topology, control, passive components, thermal management, filters, and packaging. The significance of power electronics building blocks (PEBBs) concept for shipboard power system development is discussed. Recognizing the growing complexity of shipboard power systems, some system-level technologies related to future MV direct current (dc) system architecture are highlighted.

Overview of 1.2kV – 2.2kV SiC MOSFETs targeted for industrial power conversion applications

This paper presents the latest 1.2kV-2.2kV SiC MOSFETs designed to maximize SiC device benefits for high-power, medium voltage power conversion applications. 1.2kV, 1.7kV and 2.2kV devices with die size of 4.5mm × 4.5mm were fabricated, exhibiting room temperature on-resistances of 34mOhm, 39mOhm and 41mOhm, respectively. The ability to safely withstand single-pulse avalanche energies of over 17J/cm2 is demonstrated. Next, the 1.7kV SiC MOSFETs were used to fabricate half-bridge power modules. The module typical onresistance was 7mOhm at Tj=25°C and 11mOhm at 150°C. The module exhibits 9mJ turn-on and 14mJ turn-off losses at Vds=900V, Id=400A. Validation of GEs SiC MOSFET performance advantages was done through continuous buck-boost operation with three 1.7kV modules per phase leg exhibiting 99.4% efficiency. Device ruggedness and tolerance to terrestrial cosmic radiation was evaluated. Experimental results show that higher voltage devices (2.2kV and 3.3kV) are more susceptible to cosmic radiation, requiring up to 45% derating in order to achieve module failure rate of 100 FIT, while 1.2kV MOSFETs require only 25% derating to deliver similar FIT rate. Finally, the feasibility of medium voltage power conversion based on series connected 1.2kV SiC MOSFETs with body diode is demonstrated.

Multipulse Converter - Topology and Control for Utility Power Conversion

This paper presents a novel topology highly suited for utility power conversion. The topology, referred to as the multipulse converter, uses a modular architecture, where each power module comprises a three-phase two-level bridge and a transformer. The primary windings of the transformers are wound as closed zig-zag (or polygon) and fed by a power converter, while the secondary windings of the transformers are connected in series to the utility. By selecting appropriate phase shifts between the primary and secondary sides of the transformers and synchronously switching the three-phase bridges at specified phase relations, low order harmonics can be eliminated in pairs. Thus a very high power quality voltage waveform can be synthesized using low switching frequencies. The topology supports bi-directional power flow with excellent transient control over active and reactive powers. Principle of operation, modulation strategy and control strategies are presented with validated simulation and experimental results

Universal AC input high density power adapter design with a Clamped Series Resonant Converter

In this paper, we present the design and fabrication of a high density laptop adapter with a Clamped Series Resonant Converter (CSRC), as a possible alternative to traditional Flyback converters for power adapters in portable electronics. The target is to design for universal AC input up to a power of 100 W with power density of 6-7 W/in3. The converter is frequency controlled, and all switches exhibit Zero-Current Switching (ZCS). In this paper, we show that by utilizing the magnetizing inductance, the converter can be tuned for Zero Voltage Switching (ZVS), and by adding a switched capacitor circuit to extend the input voltage range, we can realize a very compact design that is suitable for power adapters with or without power factor correction. Low transformer stresses compared to Flyback type designs enable high densities, even with a resonant magnetic. Prototype test results with a 45 W laptop adapter are presented. Our initial testing with diode rectification indicated very good efficiency. Versions with synchronous rectification promise higher efficiencies by at least 1%, which will be ideal for energy saving low power devices.