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This paper proposes a power flow control strategy based on theory of symmetrical components for implementing bi-directional power flow between the utility grid and local PV array. The system includes a three phase bidirectional inverter with a battery bank at the input interfaced through a boost converter with solar arrays. The battery bank operates in discharge mode when power is fed to the grid and charges from the grid during low demand period. For grid synchronization, principle of phase locked loop (PLL) is implemented in dq synchronous rotating frame (SRF) and PI controller has been used in the feedback loop for the necessary control. The PLL block is implemented using the concept of instantaneous symmetrical component theory. The active and reactive power flow in the grid is controlled by changing the value of reference dc voltage at the input side of inverter. The system has been simulated in PSIM software for a 1kVA inverter. This simple scheme of bi-directional power flow is useful for connecting remote areas with abundant solar energy to the local grid.

In this paper, the design guideline for a high-power-density inverter for fuel-cell (FC) applications is presented. Such an inverter can lead to savings in volume and weight due to high-frequency operation. In addition, we present a guideline to determine the optimal size of the input filter. It is also illustrated that, for such a topology, an optimal choice of transformer leakage inductance is necessary to achieve low power loss and to establish a balance between efficiency and reliability. Transient load condition, which may degrade FC-stack reliability, is handled through a battery-sourced energy-buffering unit. Experimental results demonstrating the nominal operations of inverter and energy buffering unit are presented.

This paper proposes a novel physical scalable SPICE model for Shielded-Gate Trench Power MOSFETs. The model is based on process and layout parameters, enabling design optimization through a direct link between SPICE and process technology. The model has been validated with Fairchild's state of the art technology. The model is SPICE agnostic, working seamlessly across multiple industry standard simulation platforms.

The times, they are a-changin'... Yes, there are rapid and unprecedented changes in virtually all domains of human endeavors- social interactions, business and commerce, urban migrations, global trade and communications. Advancements of science and engineering are behind many of these changes and therefore today’s young engineering professionals are increasingly being evaluated on nontraditional parameters such as teamwork and communication, project and process management, product innovation, and marketing acumen. This is indeed an uncharted territory for most graduates who have been brought up on the staple of engineering design, applied maths and physics, and conventional computer programming skills. Let me try to briefly share my own experience and touch upon key skills and approaches needed to succeed and self-develop in this turbulent and exciting time.

A potential mechanism for high-temperature integration of a recently developed GaAs-based optically triggered power transistor (OTPT) to a SiC DMOSFET for photonic control of power flow is outlined and experimentally demonstrated over a range of switching frequencies and duty cycles. It was found that the switching dynamics of the SiC DMOSFET varies with the case temperature due to a change in the conductance of the GaAs OTPT. This temperature-induced drift in the rise time of the SiC DMOSFET is compensated by a nonlinear variation in the intensity of the triggering signal of the OTPT.

Hybrid SiC pulsed-power switch (having bipolar transistor structure) with 5 kV breakdown voltage and 1 kA peak current rating has been designed, which can be triggered optically using a GaAs or SiC front-end triggering structure with a rise time < 20 ns and for sub-microsecond pulse-widths. Structural details and physics-based simulation results are presented. It is shown, that GaAs triggering structure reduces the optical-triggering power requirement significantly without sacrificing switching speed as compared to a SiC optical-triggering structure.

We outlined the epitaxial design methodology for a novel compound-semiconductor-based optically controlled power device for fast repetitive switching frequency. The proposed structure features gallium arsenide (GaAs/AlGaAs) lateral heterostructure with charge-balancing superjunction layers to make the breakdown voltage of the device independent of doping of the photo-absorbing GaAs active layer and linearly dependent on the lateral length. This structure also features parallel plate like p-n junction, which reduces local electric-field crowding and supports higher reverse bias during off-state. We show that the use of lattice-matched wider bandgap AlGaAs helps to achieve superjunction charge balancing without having any effect on switching performance of the device. We also show that the particular processing methodology (ion implantation over zinc diffusion) helps in improving the breakdown-voltage capability of the device

Optical modulation by varying the intensity, wavelength, or switching time can dynamically alter the performance parameters of direct optically controlled power semiconductor device. Understanding the effect of optical parameters on these parameters from a first principle approach is necessary for making optimal design choices and gaining design insights. We focus on performance parameters whose variations with direct optical modulation have not been reported previously for a power semiconductor such as switching times and on-state resistance. We carry out analytical modeling and two-dimensional (2D) finite-element simulations for a GaAs/AlGaAs based superjunction lateral optically controlled power transistor that has been fabricated and successfully tested for high-voltage capability. It is shown that optical power density can modulate on-state resistance and more importantly the trade-off curve between breakdown voltage and on-state resistance. A closed-form analytical equation relating switching times with optical parameters via logarithmic function is derived and the nonlinear variation of on-state resistance and switching time with optical wavelength is illustrated. We also derive the analytical expression for power device rise time as a function of optical signal rise time and show that they are related by Lambert's W-function with exponential coefficients.

Most single-phase inverters, being sourced by fuel cell stacks (FCSs), subject the stacks to reflected low-frequency (120 Hz) current ripples that ride on average dc currents. The ripple current impacts the sizing and efficiency of the FCS. As such and typically, a passive or active filter is required at the input of the inverter (or output of the FCS) to mitigate the ripple current. Toward that end, this paper outlines a guideline to choose the optimum size of a passive input-filter capacitor for a fuel-cell-based power system from the standpoints of the overall system energy density and cost. Detailed case-specific simulation results, based on an analytical approach, are provided to illustrate key issues for both unity power factor as well as harmonic loads.

Shielded-gate trench-MOSFETs yield superior performance compared to conventional gate trench devices by allowing higher doping density in the drift region and providing a `shielding effect' for the gate by placing an intermediate electrode between gate and drain. However, further design optimizations can be done for a shielded-gate trench-MOSFET to improve performance parameters particularly suited for next-generation high-frequency computing power supply applications and they have been outlined in this article. Channel length and threshold voltage optimization, substrate thinning and intrinsic gate resistance reduction (by layout enhancements) have been discussed along with their impact on device footprint reduction. Further, effects of these design optimizations on the power loss and efficiency of a high-frequency switching converter have been demonstrated through experimental characterizations.

Shielded-gate trench-MOSFETs yield superior performance compared to conventional gate trench devices by allowing higher doping density in the drift region and providing a ‘shielding effect’ for the gate by placing an intermediate electrode between gate and drain. However, further design optimizations can be done for a shieldedgate trench-MOSFET to improve performance parameters particularly suited for next-generation high-frequency computing power supply applications and they have been outlined in this article. Channel optimization, substrate thinning and intrinsic gate resistance reduction (by layout enhancements) have been discussed along with their impact on cost-performance benefit on the device. Further, effects of these design optimizations on the power loss and efficiency of a high-frequency switching converter have been demonstrated by mixed device–circuit simulations.

Novel photonic control of power semiconductor devices for next-generation power electronics applications are discussed with special emphasis on SiC DMOSFET. Key mechanism behind the photonic modulation of the switching dynamics of the SiC DMOSFET is illustrated. Specific aspects of switching loss reduction, compensation for temperature-induced drift, and on-state impedance control of the SiC DMOSFET are discussed along with experimental demonstration. Potential applications include high-power, high-frequency electronics in power systems, pulsed-power, EMI-immune, high power-density automotive and aerospace switching converters etc.

Modulation of the switching dynamics of a power semiconductor device (PSD) using an optically-triggered power transistor (OTPT), which controls the gate excitation of the PSD, is outlined and experimentally demonstrated. The core concept is the integration of width- and intensity-modulation for the optical triggering beam. Key issues related to the OTPT design, optical interfacing, and hybrid integration with the PSD die are discussed. Scalability of this concept is demonstrated across a range of PSD types (power MOSFET, IGBT, and vertical JFET) and material platforms (Si and SiC).

Critically important to the future electric ship power systems are performance and reliability parameters such as electromagnetic-noise generated by the power converter, power-conversion efficiency, and stress on the power semiconductor devices (PSDs). Modulation of these parameters using optically-modulated and galvanically isolated gate control is outlined and experimentally demonstrated. An optimal optical-intensity is also experimentally determined for balanced trade-off between switching loss reduction and PSD stress mitigation. Applicability of the concept over a wide spectrum of PSDs (including SiC MOSFET) is also demonstrated.

In this paper, the design guideline for a high-power-density inverter for fuel-cell applications is presented. Such an inverter can lead to savings in volume and weight due to high-frequency operation. Also, we present a guideline to determine the optimal size of the input filter. It is also illustrated that, for such a topology, an optimal choice of transformer leakage inductance is necessary to achieve low power loss and to establish a balance between efficiency and reliability. Transient load condition, which may degrade fuel-cell-stack reliability, is handled through a battery-sourced energy-buffering unit. Experimental results demonstrating the nominal operations of inverter and energy buffering unit are presented.

Dynamic control of electromagnetic-emission, efficiency, and stress of switching power systems using optically-modulated and galvanically isolated gate control of power semiconductor devices (PSDs) is outlined and experimentally demonstrated at a scaled power level. This is achieved by modulating the switching dynamics of a PSD using an optically triggered power transistor (OTPT), which controls the gate excitation of the PSD. An important aspect regarding scalability of the same concept towards higher power application is the controllability of the PSD onset delay (which can be optically modulated, and as demonstrated, in the proposed device concept) particularly for series/parallel connected device configurations for high voltage and current applications.

Significance of direct photonically-controlled power switching devices has been illustrated for electromagnetic-interference immune power electronics. Experimental prototype, initial characterization results, and key simulation results for III-V GaAs/AlGaAs-based optically-triggered power transistor have been shown. Superjunction charge-compensation technique and unique optical-modulation properties have been illustrated Key processing issues for high-voltage III-V epitaxial power device structure have been discussed Also, it is shown how the optical triggering idea can be extended to devices with higher gain and using wide-bandgap materials (eg, SiC).

This paper outlines the advantages of photonically-switched power electronics from the standpoint of robustness to electromagnetic interference (EMI) effects, design-ease, and system reliability. Subsequently, the principles of operation of two novel superjunction-based heterostructure optically-triggered devices are described. Satisfactory performance results of the two devices address three critical issues: wavelength of operation, electrical gain, and switching speed.

We illustrate the switching performance of a novel optically triggered power MOSFET (OT-MOS) for three different optical modulation techniques. It integrates a silicon (Si) based power MOSFET and two gallium-arsenide (GaAs) based photoconductive-triggering blocks for 'all-optical' turn-on and turn-off of the OT-MOS. We investigate the effectiveness of amplitude, pulse-width, and wavelength modulation techniques to rapidly turn-on and turn-off the OT-MOS. The OT-MOS can eliminate the problems encountered in conventional high-frequency gate drivers due to electromagnetic interference (EMI). Furthermore, the design of the gate drivers for a low- or a high-side OT-MOS, unlike a conventional electrically triggered power MOSFET, is the same; this leads to simplified gate-driver architectures for two-and multilevel power-electronic converters.