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44 results on '"Mu, Shujun"'

6. Optimization of Hydrogen Yield of a High-Temperature Electrolysis System with Coordinated Temperature and Feed Factors at Various Loading Conditions: A Model-Based Study

Author

Xing, Xuetao, Lin, Jin, Song, Yonghua, Hu, Qiang, Zhou, You, and Mu, Shujun

Subjects
Physics - Applied Physics, Computer Science - Systems and Control
Abstract

High-temperature electrolysis (HTE) is a promising technology for achieving high-efficiency power-to-gas, which mitigates the renewable curtailment by transforming wind or solar energy into fuels. Different from low-temperature electrolysis, a considerable amount of the input energy is consumed by auxiliaries in an HTE system for maintaining the temperature, so the studies on systematic description and parameter optimization of HTE are essentially required. A few published studies investigated HTE's systematic optimization based on simulation, yet there is not a commonly used analytical optimization model which is more suitable for integration with power grid. To fill in this blank, a concise analytical operation model is proposed in this paper to coordinate the necessary power consumptions of auxiliaries under various loading conditions of an HTE system. First, this paper develops a comprehensive energy flow model for an HTE system based on the fundamentals extracted from the existing work, providing a quantitative description of the impacts of condition parameters, including the temperature and the feedstock flow rates. A concise operation model is then analytically proposed to search for the optimal operating states that maximize the hydrogen yield while meeting the desired system loading power by coordinating the temperature, the feedstock flows and the electrolysis current. The evaluation of system performance and the consideration of constraints caused by energy balances and necessary stack requirements are both included. In addition, analytical optimality conditions are obtained to locate the optimal states without performing nonlinear programming by further investigating the optimization method. A numerical case of an HTE system is employed to validate the proposed operation model, which proves to not only improve the conversion efficiency but also enlarge the system load range., Comment: accepted by Applied Energy

Published
2018
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19. A Hybrid Compensation Scheme for the Gate Drive Delay in CLLC Converters

Author

Chen, Huan, Sun, Kai, Chong, Hongsheng, Zhang, Zhe, Zhou, You, Mu, Shujun, Chen, Huan, Sun, Kai, Chong, Hongsheng, Zhang, Zhe, Zhou, You, and Mu, Shujun

Abstract

The CLLC converter is often used as an isolated linker between high and low voltage buses where the CLLC converter operates under the open-loop condition at resonant frequency. In such applications, CLLC converters are able to achieve high efficiency usually due to superior performance of soft switching. However, we found that the operating process of a CLLC converter under open-loop control at the resonant frequency will significantly change by the non-ideal parameters of the semiconductor switches and gate driver circuits. These impacts on the converter operation were investigated and defined as the gate drive delay. We present a comprehensive steady-state analysis for the CLLC converter that considers the gate drive delay including its operating process, mathematical model, power loss, and voltage ripple. In some cases, the gate drive delay changes the operating process of the CLLC converter. As a result, the soft switching condition changes or even loses, large circulating current exists on the secondary side, output voltage ripples become larger and so that the efficiency decreases dramatically. Therefore, a hybrid compensation scheme, consisting of an offline design procedure and an online close-loop control algorithm, is proposed to minimize resonant frequency variation due to the gate drive delay. Both the correctness of the steady-state analysis and effectiveness of the proposed hybrid compensation scheme are verified by experiment. Using the proposed compensation scheme can reduce the output voltage ripple to 1/3 of the original value and increase the efficiency of more than 10% within the whole load range.

Published
2021

23. Universal Modulation Scheme to Suppress Transient DC Bias Current in Dual Active Bridge Converters.

Author

Mu, Shujun, Guo, Zhiqiang, and Luo, Yong

Subjects
*ZERO voltage switching, *DIGITAL signal processing, *CURRENT transformers (Instrument transformer), *DIGITAL modulation, *PULSE width modulation transformers, *BRIDGE circuits
Abstract

This article presents a modulation scheme to suppress the transient dc bias current in dual active bridge (DAB) converters. The current in the transformer at the commutating time is associated with the initial current in a switching period, so there must be a dc bias current during the transient response. To investigate the modulation scheme for suppressing the transient dc bias current, the article reviews the optimal TPS control strategy, which is derived from the zero voltage switching with the minimum current stress in the transformer. By analyzing the dc bias current, the transient dc bias current can be evaluated by the current in the transformer at the symmetry line of the primary full-bridge voltage waveform instead of the current at the commutating time. It can be concluded that the expressions of the transient dc bias current for different working modes are unified. Therefore, the modulation schemes without transient dc bias current for different working modes can be also unified. On this basis, a universal strategy can meet all the transient cases. There is no need to identify or select the working modes and power conditions in the transient dc bias current control, which simplifies the implementation of the modulation scheme in the digital signal processor. Finally, an experimental prototype has been built to verify the effectiveness of the proposed modulation scheme. [ABSTRACT FROM AUTHOR]

Published
2022
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26. Loss Comparison of Two Bidirectional Isolated DC/DC Converters for Reversible Solid Oxide Fuel Cell Systems

Author

Zhou You, Lin Xiang, Qu Keqing, Mu Shujun, Sun Kai, and Kong Wei

Subjects
Materials science, business.industry, 020208 electrical & electronic engineering, Topology (electrical circuits), Port (circuit theory), 02 engineering and technology, Converters, Network topology, Topology, Stack (abstract data type), Cascade, Computer data storage, 0202 electrical engineering, electronic engineering, information engineering, Solid oxide fuel cell, business
Abstract

The reversible solid oxide fuel cell (RSOFC) is a promising solution for future storage system in power grid, but the wide voltage range makes it difficult to design the DC/DC converter for RSOFC stack. In this paper, the losses of two DC/DC topologies, CLLC cascade interleaved Buck(two-stage) converter and dual-active-bridge(DAB) converter, are compared as the interface DC/DC converter for RSOFC. Firstly, the topology and control method is introduced for two selected DC/DC converters. Secondly, the losses of two converters are analyzed and corresponding loss models are presented. The loss models are also extended for multi-port topology. At last based on 1kW single port prototype, the experiments are conducted and the total loss are measured for two topologies. Both the model and experimental results indicate that the two-stage topology has higher efficiency and is selected for the interface DC/DC converter for RSOFC stack.

Published
2018

31. A Variable Pole Pitch Linear Induction Motor for Electromagnetic Aircraft Launch System

Author

Chai Jianyun, Wang Shanming, Mu Shujun, and Sun Xudong

Subjects
Electric motor, Nuclear and High Energy Physics, business.industry, Computer science, Electrical engineering, Topology (electrical circuits), Thrust, Converters, Condensed Matter Physics, Power (physics), Acceleration, Control theory, Linear induction motor, business, Induction motor
Abstract

A variable pole pitch linear induction motor (VPPLIM) is proposed as a new member of the family of electromagnetic aircraft launch system (EMALS). With proper designing of the variation of the pole pitch, the VPPLIM could accelerate the aircraft almost uniformly at the condition of the usual ac supply, avoiding the use of large-scale power electronic converters. Special considerations in the design of VPPLIM, such as the structure topology, the variation of the pole pitch, and the winding arrangement are discussed in detail in this paper. The acceleration performance of the VPPLIM fed by a constant-voltage constant-frequency supply is analyzed by means of the quasi-steady-state 2-D magnetic field model and the difference model of mover's dynamics. A two-stage method is proposed to simulate the acceleration performance of the VPPLIM based on a 2-D thrust table of the motor achieved by the finite-element method. The calculated features of the prototype VPPLIM consist well with those expected for EMALS.

Published
2015

32. A curtailed wind power accommodation strategy based on wind-hydrogen-heat-storage integrated energy network

Author

Sun Kai, Zhou You, Mu Shujun, Lin Jin, Zhang Ding, and Yang Ye

Subjects
Wind power, business.industry, 020209 energy, 02 engineering and technology, Thermal energy storage, Automotive engineering, Energy storage, Electric power system, Cogeneration, Electricity generation, 0202 electrical engineering, electronic engineering, information engineering, Environmental science, Electricity, Electric power, business
Abstract

The wind power curtailment issue has been recognized extensively and it can't be solved by upgrading the electric power alone. Meanwhile, the chemical or physical energy storage system, like battery-storage or pumped-storage, are also not able to solve the issue cost-effectively due to either economical or geographical limitations. This paper adopts hydrogen and heat as energy storage media to alleviate the wind power curtailment issue. Based on hydrogen production by electrolysis of water, power generation by fuel cell and methane synthesis from hydrogen and carbon dioxide, the electricity, gas and heat can be integrated in one network. In another word, a ‘wind-hydrogen-heat-storage’ integrated energy network can be formed sophisticatedly. Based on the integrated energy network, a curtailed wind power accommodating strategy will be presented specifically. Detailed realization methods of the integrated energy network and operation modes of the proposed accommodating strategy will also be discussed in the paper. The results can prove that the curtailed wind power accommodating strategy is able to greatly increase the absorptive capacity of the abandoned wind power.

Published
2017

33. Status of an MWthintegrated gasification fuel cell power-generation system in China

Author

Wei, Chang, Liu, Zhien, Li, Chufu, Singh, Surinder, Lu, Haoren, Gong, Yudong, Li, Pingping, Wang, Hanlin, Yang, Xia, Xu, Ming, and Mu, Shujun

Abstract

Here, we provide a status update of an integrated gasification fuel cell (IGFC) power-generation system being developed at the National Institute of Clean-and-Low-Carbon in China at the megawatt thermal (MWth) scale. This system is designed to use coal as fuel to produce syngas as a first step, similar to that employed for the integrated gasification combined cycle. Subsequently, the solid-oxide fuel-cell (SOFC) system is used to convert chemical energy to electricity directly through an electrochemical reaction without combustion. This system leads to higher efficiency as compared with that from a traditional coal-fired power plant. The unreacted fuel in the SOFC system is transported to an oxygen-combustor to be converted to steam and carbon dioxide (CO2). Through a heat-recovery system, the steam is condensed and removed, and CO2is enriched and captured for sequestration or utilization. Comprehensive economic analyses for a typical IGFC system was performed and the results were compared with those for a supercritical pulverized coal-fired power plant. The SOFC stacks selected for IGFC development were tested and qualified under hydrogen and simulated coal syngas fuel. Experimental results using SOFC stacks and thermodynamic analyses indicated that the control of hydrogen/CO ratio of syngas and steam/CO ratio is important to avoid carbon deposition with the fuel pipe. A 20-kW SOFC unit is under development with design power output of 20 kW and DC efficiency of 50.41%. A 100 kW-level subsystem will consist of 6 × 20-kW power-generation units, and the MWthIGFC system will consist of 5 × 100 kW-level subsystems.

Published
2021
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43. A novel linear induction motor for electromagnetic aircraft launch system

Author

Chai Jianyun, Mu Shujun, Sun Xudong, and Wang Shanming

Subjects
Engineering, Acceleration, business.industry, Control theory, Electromagnetic coil, Linear induction motor, Topology (electrical circuits), Thrust, business, Synchronous motor, Induction motor, Finite element method
Abstract

A variable pole pitch linear induction motor (VPPLIM) is proposed as a new member of the family of electromagnetic aircraft launch system (EMALS). With proper designing of the variation of the pole pitch, the VPPLIM could accelerate the aircraft almost uniformly at the condition of usual AC supply, avoiding use of large scale power electronics converters. The special considerations in the design of VPPLIM, such as the structure topology and the variation of the pole pitch are discussed detailedly in the paper. The acceleration performance of the VPPLIM fed by a constant voltage constant frequency supply is analyzed by means of the quasi-steady-state 2D magnetic field model and the difference model of mover's dynamics. A two stage method is proposed to simulate the acceleration performance of the VPPLIM based on a 2D thrust table of the motor achieved by finite element method (FEM). The calculated features of the prototype VPPLIM consist well with those expected for EMALS.

Published
2014

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