Tianjin, China
Tianjin, China

Tianjin University is a national university under the direct administration of the Ministry of Education of China. It is the first modern higher education institution in China. It was established in 1895 as Tientsin University/Imperial Tientsin University and later Peiyang University . In 1951, after restructuring, it was renamed Tianjin University, and became one of the largest multidisciplinary engineering universities in China. The university was one of the first 16 universities accredited by the State in 1959. It is also among the first group of institutions of higher learning in the national “211-Project” to which priority is given in construction. In order to carry out the “21st Century Education Revitalizing Action Plan”, in late 2000 the Ministry of Education and Tianjin Municipality signed an agreement which aims to build Tianjin University into a world famous university in the 21st Century. Wikipedia.

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Zhao B.,Zhejiang Electrical Power Test and Research Institute | Zhang X.,Zhejiang Electrical Power Test and Research Institute | Chen J.,Tianjin University
IEEE Transactions on Power Systems | Year: 2012

The paper presents an integrated microgrid laboratory system with a flexible and reliable multimicrogrid structure; it contains multiple distributed generation systems and energy storage systems and integrates with a diesel generator that serves as a back-up power source and flywheel energy storage for fast balancing to provide uninterruptible power-supply services in cooperation with the diesel generator. The microgrid system, by adopting the master-slave control strategy, can be transited flexibly between grid-connected and islanded modes and can be disconnected from the utility when a fault occurs or the power quality falls below specified standards. The developed bi-directional inverter which is applied in the system plays an important role. The small microgrids of this system are intended to operate separately or in the form of one large microgrid with a certain switch status. Furthermore, experiments on control, protection, and other technologies have been carried out. The results show that the operation conditions meet the related IEEE Standard 1547 and power quality requirements. The integrated microgrid laboratory system is able to operate stably and reliably under different conditions, including mode transition and fault events. © 1969-2012 IEEE.

Document Keywords (matching the query): flywheel energy storage.

Chen W.,Tianjin University | Yin H.,Tianjin University
Clean Technologies and Environmental Policy | Year: 2016

Distributed renewable energy generation via micro-grid plays a strategic role in defining energy policy for mitigating the pressure of global climate changes and energy reservation. As the initial installation of the renewable generation equipment is costly, it is necessary that the government provides incentive schemes to private investors aiming at mobilizing private capital to support distributed renewable energy generation. This paper brings forward optimal subsidy to stimulate private investment and focuses more on the government’s expected policy benefit. We formulate principal–agent model in which the private investor’s preference toward renewable generation is described as asymmetric information. We analyze the optimal subsidy with the purpose of maximizing the expected policy benefit; besides, this paper reveals benefit conflicts between the policymakers and the private investors, and examines the parameters’ effect on the government’s purpose under the condition of asymmetric information. Finally, a numerical example is presented to test the effectiveness of the model. The results shed new light on the role of investor’s preference in determining the share of renewable energy generation; moreover, it has important implication for policymakers: the results suggest that radically innovative systems will get down the cost curve and may display higher long-term potentials, but in the short run, the government should eliminate asymmetric information as far as possible and improve the investors’ environment-friendly awareness. © 2016 Springer-Verlag Berlin Heidelberg

Document Keywords (matching the query): distributed generation, renewable energy generation, distributed power generation, renewable generation, renewable energy resources, distributed renewable energy generations.

Bei T.-Z.,Tianjin University | Wang P.,Tianjin University
IET Generation, Transmission and Distribution | Year: 2016

The distributed power generation networks and smart grids are characterised by a high penetration of renewable energies. For purposes of improving the power quality of the distributed generation and achieving a reliable, efficient and safe operation of the grid, on the basis of the synchronisation techniques, this study proposes a robust frequency-locked loop (FLL) algorithm for grid synchronisation of single-phase applications under distorted grid conditions. The algorithm mainly includes a frequency-adjustable quadrature signal generator (QSG) and a cascaded adaptive complex filter (ACF), as well as a robust frequency adaptive controller. The suggested QSG can generate two-phase orthogonal voltages with the same attenuation ratio. In the proposed scheme, the normalised blocks and the cascaded ACF are introduced, for purposes of eliminating the influence of voltage fluctuation and the harmonics on the frequency adaptive adjustment effectively. Theoretical analysis indicates that the proposed FLL algorithm has good performance in aspects of rapidity and robustness even in the hostile envelopments caused by frequency variation, voltage fluctuation and harmonic distortion. Simulations and experimental results are provided at the end of this study to validate the good performance of the proposed algorithm. © The Institution of Engineering and Technology 2016.

Document Keywords (matching the query): renewable energies, distributed power generation.

Wang C.,Tianjin University | Li P.,Tianjin University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

The key points, difficulties, and developments of distributed energy resources and energy efficiency as seen at the 21st International Conference on Electricity Distribution (CIRED 2011) are presented. The introduction mainly focuses on four directions, i.e. distributed generation (DG)/distributed energy resource (DER) planning and studies, control of networks with DG/DER, customer side development and DG/DER technology. These topics are hoped to help engineers and researchers widen their vision in related research fields and deepen their understanding of the problems, opportunities, and challenges faced by the distribution system, and finally to promote the R&D and engineering application of smart grid technologies in China. © 2012 State Grid Electric Power Research Institute Press.

Document Keywords (matching the query): energy efficiency improvements, distributed generations, energy resources, distributed energy resources, distributed energy resource, distributed power generation, energy efficiency, distributed energy resource der, distributed generation dg.

Wang C.,Tianjin University | Wu Z.,Tianjin University | Li P.,Tianjin University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2014

Microgrid is an effective way to make full use of distributed energy resources. It has great significance to both economy and society. Due to the variety of distributed energy resources and the complicated operation modes of microgrid, the planning, operation, protection, control, simulation and experiment of microgrid are quite distinct from traditional power system. Critical issues and current status of the key technologies in microgrid study are elaborated in detail. The future trends of microgrid research are also discussed.

Document Keywords (matching the query): distributed generation, distributed energy storages, energy resources, distributed power generation, distributed energy storage, distributed energy resources.

Wang C.,Tianjin University | Li X.,Tianjin University | Guo L.,Tianjin University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

As the key units for energy resources integration and power conversion, two-stage power converters containing DC/DC and DC/AC modules have been experiencing wide application in PV, the lithium battery energy storage systems and other distributed generations (DGs) and microgrids, which require coordinated control to ensure their operation stable. In this paper, the parameters of DC/DC and DC/AC controllers were designed respectively via classical control theory; in addition, the small-signal stability analysis was presented through eigenvalue theory based on the state-space model; moreover, a combination feedforward method of power balancing and time-delay compensation (a first derivative element) had been proposed, with the purpose to eliminate/minimize the DC bus voltage fluctuations and impact on the DC bus capacitor. Experimental results indicate that the system dynamic and steady performances obtained are consistent with the theoretical analysis, and the improved feedforward compensation method can effectively suppress transient voltage fluctuations and impact on the DC bus capacitor, and speed up system dynamic response. © 2012 Chinese Society for Electrical Engineering.

Document Keywords (matching the query): battery energy storage systems, energy resources, distributed generations dgs, distributed power generation, distributed generation dg.

Tan Z.,Tianjin University | Li Y.-L.,Tianjin University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

In order to utilize renewable energy efficiently and overcome their inherent intermittent and unpredictable nature, it is necessary to construct micro grids not only with distributed generation and load, but also with energy storage units. To solve the problems of permanent magnet brushless DC motor control and energy conversion in a flywheel energy storage system, a bi-directional DC-DC power conversion circuit is designed and its dual-PI closed-loop control strategy is proposed. Under theoretical analysis and simulation, a control platform based on dual-DSP is developed to accomplish the control tasks in charging and discharging processes. On the experimental system of flywheel energy storage, charging and discharging experiments are carried out. The flywheel accelerates smoothly to the target speed and maintains the constant speed when charging, and it can achieve a constant voltage discharging on the load. Results show the effectiveness of both control platform and control strategy.

Document Keywords (matching the query): renewable energy, energy conversion, distributed power generation, flywheel energy storage, energy storage, renewable energies, flywheel energy storage system, energy storage unit.

Wang C.,Tianjin University | Li P.,Tianjin University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

The basic concepts and development trend of distributed generation (DG), the micro-grid and smart distribution system are described. In particular, the influence of DG and micro-grid on the smart distribution system is analyzed from the point of view of the large-scale access of distributed energy resources. DG supplies users with green power from various locally available renewable energy resources, but large-scale interconnected operation of DG in the distribution system may give rise to security and operation problems. Micro-grid technology provides an interface to the interconnection of various DGs by means of structures at different levels, which is the most efficient way for the operation of DG. On the other hand, the smart distribution system makes it possible to realize flexible access to DG and safe, reliable, and optinal operation of the entire power system by effectively managing the micro-grids. Based on an analysis of the relationship between the three, suggestions about the idea and technical means are given for implementing the smart distribution system. ©2010 State Grid Electric Power Research Institute Press.

Document Keywords (matching the query): distributed generation, distributed generations, mesh generation, distributed energy resources, distributed parameter networks, renewable energy resources, distributed generation dg.

Fu L.,Tianjin University | Wang S.,Tianjin University | Zhang Y.,Weifang Electrical Power Company | Zhang C.,Weifang Electrical Power Company | Dong P.,Weifang Electrical Power Company
Dianwang Jishu/Power System Technology | Year: 2012

The key element to determine whether distribution generator (DG) can achieve better results or not is to reasonably select and configure various types of DGs during the planning process of distributed generation system. For this purpose, firstly the output models of various DGs are built; then taking meeting the demand of load growth and minimizing the present value of annual total programmed cost of power supply company in which the environmental effects are considered as optimization objectives, the simulation analysis on distributed generation system containing various DGs such as wind power generation, photovoltaic power generation and combined cooling, heating, and power (CCHP) by micro-gas turbine is performed, and the sensitivity analysis on three variables, namely the wind speed, the price of natural gas and the punishment criteria, is conducted; finally, the optimal selection and configuration results for distributed generation system is achieved. The obtained results are available for reference to the planning for large-scale urban DG projects and the decision-making of installing individual DG system.

Document Keywords (matching the query): solar energy, distributed generation system, distributed generators, distributed power generation, photovoltaic power generation, distributed network, distributed generator dg.

Tianjin University | Date: 2014-04-04

The present invention belongs to the field of utilization of distributed power generations and smart power management and, relates to an electric power router with multiple power supply modes; it includes a control unit, a communication module, a bidirectional alternate/direct current converter, a switch array, a direct current power line, two alternate current power lines, a power line measuring module, and router ports; wherein, the router ports include a plurality of power source ports and load ports; the switch array includes a single throw switch for grid connection and a plurality of double throw switches, all of which are controlled by the control unit; the direct current power source ports of the router ports are connected to the direct current power line, the direct current power line is connected to the second alternate current power line through the bidirectional alternate/direct current converter; the alternate current power source ports and load ports are connected through two alternate current power lines and the switch array. The present invention enables highly effective and smart management to kinds of power sources and loads, according to the power supplying condition of the power sources as well as the power consumption characteristics and consumption demands of the loads.

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2. The electric power router according to claim 1, wherein, the power sources other than the grid power connected to the electric power router with multiple power supply modes have three operation modes: the grid tied operation, islanded operation, and parallel operation; 1) in case all the loads connected to the electric power router are powered by the direct current power line and second alternate current power line, and the power supply from the power sources other than the grid power is surplus, the second alternate current power line is connected with the first alternate current power line through the single throw switch for grid connection so that the electric power router is working in grid tied operation mode; 2) when grid power is cut off, all the loads are connected to the direct current power line or to the second alternate current power line via the double throw switches of the switch array, all the loads connected to the electric power router are powered by the power sources other than the grid power or the energy storage element connected with the power router, which is the islanded operation; 3) when the grid power is connected to the electric power router and the single throw switch for grid connection is switched off, the second alternate current power line is disconnected with the first alternate current power line, but both alternate current power lines supply power to the loads via the double throw switches of the switch array, in this case, the energy storage element and the power sources other than the grid power, along with the grid power itself, supply power to different loads simultaneously through the electric power router, which is the parallel operation mode; during above processes, operations including connection, disconnection and shifting of any one of the switches of the switch array are controlled by the control unit.

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