Engineering topics
Feng, Xianyong
Publications and source records attributed to Feng, Xianyong.
Influences on hydrogen production at a wind farm
If an affordable infrastructure for low-carbon-intensity hydrogen can be developed, then hydrogen is expected to become a key factor in decarbonizing the atmosphere. This research focuses on factors an existing wind farm operator would consider when weighing participating in the electricity market, the hydrogen market, or both. The solutions depend on the state of technology, which is changing rapidly, the local market structures, the local natural resources, and the local pre-existing infrastructure. Consequently, this investigation used an assessment approach that examined the variation of net present value. The investigation identified profitability conditions under three different scenarios: 1) Make and sell what makes economic sense at the time of production, 2) Use electrolyzer and fuel cell to consume power from the grid at times of low net demand and to produce electricity at times of high net demand, 3) Same as #2 but also market hydrogen directly when profitable.
Real-time Implementation of a Dual-Active-Bridge Based Multi-Level Photovoltaic Converter
Silicon-carbide based, multi-level converters with dual-active-bridge (DAB) are getting attention for medium voltage, direct grid-connected, utility-scale photovoltaic (PV) applications due to their higher efficiency and power density. To de-risk complex control development for these high-voltage and high-power inverters, hardware-in-the-loop techniques are often required. Due to the high switching frequency and the large number of power electronic switches, off-the-shelf, real-time simulation tools are not yet fully developed for this application, even with FPGA-based simulators. To address this, a new co-simulation approach in FPGA is presented that utilizes Time-Stamped Bridge (TSB) for the higher frequency converters along with detailed fixed conductance based discrete device simulation of the rest of the circuit. A complex DAB-based PV converter with maximum switching frequency of 50 kHz is successfully simulated in real-time in the FPGA and the results are compared with offline simulation results. A controller hardware-in-the-loop (CHIL) platform is developed to demonstrate real-time, closed-loop test results for this DAB-based PV converter.
Design and Optimization of a 200-kW Medium-Frequency Transformer for Medium-Voltage SiC PV Inverters
This paper presents a design and optimization methodology for a 200-kW medium-frequency transformer (MFT) based on low-loss magnetic core (FINEMET FT-3TL). The proposed optimal design methodology consists of predesign, preliminary design, and optimal design. In the preliminary design, the parallel-concentric winding structure is selected to increase the current carrying capability and reduce the leakage inductance. Based on the parallel-concentric winding concept, a novel cooing and insulation structure with 3-D printed bobbins are proposed. The optimal designed MFT prototype achieves a power density higher than 19.23 kW/L. The electrical insulation system is tested at 12 kV ac peak voltage. In addition, the partial discharge (PD) test is conducted at 7.5 kV ac peak voltage to ensure the PD-free design. The high-frequency bipolar pulsewidth modulation voltage insulation (PD) test is the first time applied in MFT design and test process. Finally, the transformer is applied in a dual-active-bridge (DAB) converter with 200 kW rated power. The peak efficiency of the DAB converter is 99.53%, and the efficiency at 200 kW is 98.85%. The peak efficiency of MFT is 99.844%, and the efficiency at 200 kW is 99.842%.
Islanding Detection in Rural Distribution Systems
This paper summarizes the literature on detection of islanding resulting from distributed generating capabilities in a power distribution system, with emphasis on the rural distribution systems. It is important to understand the legacy technology and equipment in the rural distribution electrical environment due to the growth of power electronics and the potential for adding the new generations of intelligent sensors. The survey identified four areas needing further research: 1. Robustness in the presence of distribution grid disturbances; 2. the future role of artificial intelligence in the islanding application; 3. more realistic standard tests for the emerging electrical environment; 4. smarter sensors. In addition, this paper presents a synchro-phasor-based islanding detection approach based on a wireless sensor network developed by the University of Texas at Austin. Initial test results in a control hardware-in-the-loop (CHIL) simulation environment suggest the effectiveness of the developed method.
Model Validation and Demonstration of a Hydrogen Fuel Cell Parcel Delivery Truck
With an emphasis on reducing fossil fuel consumption and emissions, major delivery service corporations have begun deploying and operating Class 6 battery electric delivery vans. Fuel cell hybrid delivery vans offer a zero emissions solution with extended range and route planning flexibility. This paper follows a prior publication [1] on the vehicle modeling and design and presents demonstration data and a validation of the prior modeling and design effort. Here, the validation exercise shows that the modeling tools predict performance and energy efficiency within 5% for most of the routes, while the demonstration data shows that in service operation fuel economy was over 14 km/kg of hydrogen gas. In addition, results from a range test showed the vehicle design and onboard hydrogen storage was able to surpass the design target range of 200 km.