Solar Panel Companion Inverter (SPCI) is a single stage DC-AC power converter, installed behind each solar panel. Each SPCI synthesizes an AC quasi-square wave voltage with variable pulse width. Width of AC output voltage of each SPCI is proportional to available power on the solar panel. Output voltages of SPCIs are aggregated across multiple solar panels connected in series, and a sinusoidal AC voltage is synthesized. In this paper, dynamic analysis and closed loop current controller design of SPCI is presented. Simulation results demonstrating the dynamic response of the closed loop SPCI is presented. The closed loop current control scheme is implemented on a hardware prototype to demonstrate the grid tied operation of SPCI, and experimental results are presented. Maximum Power Point Tracking (MPPT) algorithm is implemented for Sorted Stair Case Modulation (SSCM) in MATLAB Simulink. Experimental results demonstrating MPPT operation are presented.

This paper proposes a novel concept for an electric generator in which both ac windings and permanent magnets (PMs) are placed in the stator. Concentrated windings with a special pattern and phase coils placed in separate slots are employed. The PMs are positioned in a spoke-type field concentrating arrangement, which provides high flux intensification and enables the use of lower remanence and energy non-rare earth magnets. The rotor is exterior to the stator and has a simple and robust reluctance-type configuration without any active electromagnetic excitation components. The principle of operation is introduced based on the concept of virtual work with closed-form analytical airgap flux density distributions. Initial and parametric design studies were performed using electromagnetic FEA for a 3MW direct-drive wind turbine generator employing PMs of different magnetic remanence and specific energy. Results include indices for the goodness of excitation and the goodness of the electric machine designs; loss; and efficiency estimations, indicating that performance comparable to PM synchronous designs employing expensive and critical supply rare-earth PMs may be achieved with non-rare earth PMs using the proposed configuration.

This paper presents a large-scale multi-objective design optimization for a direct-drive wind turbine generator concept that is based upon an experimentally validated computational model for a small-scale prototype motor of the same type. By integrating an outer reluctance -type rotor and a segmented stator with toroidally wound single-coil modules containing spoke -type PMs, the design optimization aims to minimize losses, active mass, and torque ripple while adhering to a power factor constraint. The AC windings and PMs are positioned in the stator and this concept enhances flux concentration, enabling the use of more affordable high energy non-rare- earth (special type) magnets. The exterior rotor follows a simplified reluctance -type configuration, eliminating active electromagnetic components. The operational principle, described in detail, guides design studies using electromagnetic 2D finite element analysis (FEA), showcasing the potential of this configuration to match rare- earth PM performance, with special type PMs, thus addressing cost and supply challenges. Furthermore, alternative materials including the substitution of aluminum wire for copper wire, have also been investigated in this study. The proposed multi-objective design optimization uses the response surface method (RSM) to initiate the optimization and the results on a 3MW, 15 rpm generator, highlight the benefits of this topology, achieving competitive metrics like goodness, specific thrust, and efficiency without rare- earth permanent magnets.

In conventional medium-voltage solid-state circuit breakers (SSCBs), series-connected semiconductor switches are used with metal oxide varistors (MOVs) in parallel with each of them to extend the voltage ratings of the breakers without incurring the dynamic voltage unbalance. Besides, for isolating the faults at faster speeds, the clamped surge voltages of the MOVs are always much higher than the system voltages. For those reasons, the voltage ratings of all the switches in the SSCBs have to be overdesigned according to the surge voltage values, which causes high material costs along with nonideal conduction losses in the SSCBs employed for medium-voltage dc distribution systems. To solve this dilemma, a surgeless diode-clamped multilevel SSCB is proposed in this article. It offers an ultrafast isolation speed with no significant surge voltages or dynamic unbalanced voltage across the semiconductor switches. With these attributes, the proposed SSCB can potentially use the semiconductor switches rated at lower voltages compared to conventional SSCBs and have higher efficiency along with faster isolation speed. The simulation and experimental results are presented to validate the technical feasibility and practical values of the proposed SSCB.

Since the introduction of wide-bandgap (WBG) power semiconductor devices, high power density (PD) inverter design has become an increasingly popular topic in modern research literature. The 2014-2015 Little Box Challenge (LBC) cosponsored by Google and the IEEE sparked even more interest in this area because WBG-based designs aspired to achieve upward of 215-W/in ³ power densities. This article reviews several key topics of importance that are related to realizing such high PD gallium nitride (GaN) WBG-based inverter designs. More specifically, this article includes a comprehensive survey of technologies employed by participating LBC finalists in their efforts to achieve new levels of PD in 400-Vdc to single-phase 240-Vac conversion applications while maintaining tight specifications on dc ripple, ac ripple, and aggressive requirements on efficiency. Both singlephase dc-to-ac conversion and the related active energy buffer circuit topologies used by all LBC finalists are documented and compared. Additionally, a graphical trend line and figure of merit (FOM) are developed that compare PD vis-?-vis efficiency of all proposed solutions. These are used to gain insight into how particular designs were able to achieve relatively higher PD levels and to illustrate how the GaN-based design from the University of Illinois at Urbana-Champaign (UIUC) was able to achieve the highest density power conversion in this competition. Furthermore, enhanced auxiliary devices and techniques used in the CE+T and Virginia Tech (VT) designs are discussed as well.