This paper presents the power loss model analysis and efficiency of three-level neutral-pointclamped (3L-NPC) inverter that is widely employed in solar photovoltaic energy conversion system. A silicon carbide (SiC) 3L-NPC inverter is developed in this paper by employing wide bandgap semiconductor power devices, such as SiC MOSFET and SiC diode (SiC D). These devices are used due to their superior characteristics over silicon (Si) semiconductor devices for the reduction of inverter power losses, and as a result, an improving efficiency at the high switching frequency. Accurate and detailed power loss calculation formula and power loss distribution over switching devices of the SiC 3L-NPC inverter are derived according to the modulation technique and inverter operation. The switching energy loss of SiC MOSFET is then measured and determined experimentally via inductive clamp double pulse test (DPT) at the real working condition of the circuit. Afterward, this experimental data is used in the thermal description file of the device's library of PLECS simulation software to determine the total power loss of SiC 3L-NPC inverter. The developed simulation model replicates the real operating conditions of the 3L-NPC inverter. This method gives results close to the practical test. Finally, the power loss of SiC 3L-NPC inverter is measured and compared with the theoretical results. Furthermore, SiC MOSFET and SiC D are employed to achieve high system efficiency at the high switching frequency. The results verify the features of SiC 3L-NPC inverter, the corresponding modulation technique used and their effects on reducing and improving power loss in solar SiC photovoltaic inverters. INDEX TERMS Three-level neutral-point clamped inverter (3L-NPC), SiC MOSFET, power loss, DPT-double pulse test, PLECS.

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In association with the development of intermittent renewable energy generation (REG), dynamic multiobjective dispatch faces more challenges for power system operation due to significant REG uncertainty. To tackle the problems, a day-ahead, optimal dispatch problem incorporating energy storage (ES) is formulated and solved based on a robust multiobjective optimization method. In the proposed model, dynamic multistage ES and generator dispatch patterns are optimized to reduce the cost and emissions. Specifically, strong constraints of the charging/discharging behaviors of the ES in the space-time domain are considered to prolong its lifetime. Additionally, an adaptive robust model based on minimax multiobjective optimization is formulated to find optimal dispatch solutions adapted to uncertain REG changes. Moreover, an effective optimization algorithm, namely, the hybrid multiobjective Particle Swarm Optimization and Teaching Learning Based Optimization (PSO-TLBO), is employed to seek an optimal Pareto front of the proposed dispatch model. This approach has been tested on power system integrated with wind power and ES. Numerical results reveal that the robust multiobjective dispatch model successfully meets the demands of obtaining solutions when wind power uncertainty is considered. Meanwhile, the comparison results demonstrate the competitive performance of the PSO-TLBO method in solving the proposed dispatch problems.

Renewable energy resources (RERs) play a vital role in reducing greenhouse gases, as well as balancing the power generation demand in daily life. Due to the high penetration of RERs and non-linear loads into utility power systems, various power quality issues arise, i.e., voltage drop, harmonic distortion, reactive power demand, etc. In order to handle these power quality issues, there is a need for smart flexible alternating current transmission system (FACTS) devices. In this paper, a super capacitor energy storage system (SCESS)-based static synchronous compensator (STATCOM) is designed in order for the grid-connected photovoltaic (PV) system to overcome the abovementioned power quality issues. A voltage controller and a d-q axis controller are used for the efficient performance of the STATCOM. In order to show the superiority of the supercapacitor, a detailed comparison is made between a battery energy storage system (BESS)-based STATCOM and a SCESS-based STATCOM. Four scenarios are studied to evaluate the performance of the proposed STATCOM design. The proposed SCESS-based STATCOM not only boosts the voltage but also stabilizes it from 368 V to 385 V (Ph-Phrms). The simulated results have confirmed that the proposed design is not only superior to a BESS-based STATCOM but also has the capability to overcome the power quality issues as well.

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