Hangzhou, China

Zhejiang University

www.zju.edu.cn/
Hangzhou, China

Zhejiang University , sometimes referred to as Zheda, is a national university in China. Founded in 1897, Zhejiang University is one of China's oldest institutions of higher education. It is a member of the C9 League and Yangtze Delta Universities Alliance. The university campus is located in the city of Hangzhou, approximately 112 miles southwest of Shanghai. Zhejiang University Library collection contains about 7 million volumes, making it one of the largest academic libraries in the country. Wikipedia.

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Yu K.,Zhejiang University | Cao Y.,Zhejiang University | Chen X.,Hohai University | Guo C.,Zhejiang University | Zheng H.,Hohai University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2011

The power flow in the district grid varies with some randomicity especially distributed generations are integrated, such as wind power generation, photovoltaic generation etc. According to the laws and the stochastic waving of the changes of wind energy, solar energy and electric power load, dynamic random variable was defined and its probability model was built by integrating the laws of the changes and random variable. The numeric characteristics of the dynamic random variable were calculated by simple calculation based on using semi-invariant. And its probability density function was estimated through the approximate method on Gram-Charlier progression. Simulation tests were carried out on data of a district grid. The result indicates that the probability model of the dynamic random variable can comprise the laws and the stochastic waving. And the calculation method of dynamic probability power flow presented in this paper is feasible. © 2011 Chin. Soc. for Elec. Eng.

Document Keywords (matching the query): solar energy, distributed generation, distributed power generation, solar power generation, photovoltaic generation, wind energy.


Wu W.,Shanghai Maritime University | He Y.,Shanghai Maritime University | Geng P.,Shanghai Maritime University | Qian Z.,Zhejiang University | Wang Y.,Zhejiang University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2012

DC micro-grids, as a self-management grid form of integrating distributed energy systems with utility power systems, will realize the value and benefit of the distributed energy resources efficiently and have a more flexible capability of reconfiguration. However, the barriers of its effective promotion are both the struggling quench of the DC current arc and the lack of common standards and guidelines, leading to a long conversion process mixed with conventional AC technologies and novel DC approaches. This paper presents a comprehensive overview of the current key technologies for DC micro-grid, including control, protection, netting modes, communication, power electronic converters, presenting with a goal of identifying DC micro-grid better. In the end, combined with China's actual power system conditions, it is proposed a tailor-made scheme brought into the residential sub-districts in cities.

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


Wang M.,Zhejiang University | Tian Y.,Zhejiang University | Li T.,Zhejiang University | Li T.,Korea University | Chen G.,Zhejiang University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2013

Distributed energy has been widely developed and applied. Distributed generations(DGs) are mostly unstable electric sources, so a unified model in which energy storage systems are connected to the DC bus is proposed in this paper. Energy storage unit can stabilize energy fluctuation of DGs and improve power qualities. It is connected to DC bus through interleaved bidirectional DC/DC converter. In traditional occasions the inductor ripple of bidirectional DC/DC converters tend to be high and the inductor current of different phase are usually unbalanced. This paper proposes a novel phase-shifted current sharing control strategy to solve these problems. Experimental results are conducted to validate the effectiveness of the proposed strategy.

Document Keywords (matching the query): distributed generation, energy storage systems, distributed generations dgs, energy fluctuation, distributed energies, distributed power generation, energy storage, energy storage unit.


Zhang S.,Zhejiang University | Huang M.,Zhejiang University
2011 International Conference on Electrical and Control Engineering, ICECE 2011 - Proceedings | Year: 2011

Growing concern for environmental issues poses significant chance to utilization of distributed renewable energy resource. The intermittent nature of renewable energy put power system at risk. Microgrid is introduced as a strategy to integrate renewable energy resource from various locations with power system. Eventually, Microgrid Renewable Energy Utilization Mechanism is proposed to provide an institutional guarantee and a trading platform for renewable energy resource utilization in the units of microgrid. © 2011 IEEE.

Document Keywords (matching the query): distributed generation, renewable energy, distributed power generation, microgrid renewable energy utilization mechanism, renewable energy resources, energy utilization, renewable energies.


Zeng Z.,Zhejiang University | Yang H.,Zhejiang University | Zhao R.,Zhejiang University
Renewable and Sustainable Energy Reviews | Year: 2011

Microgrid is an effective concept for distributed renewable energies connecting to utility grid. However, enormous challenges have also been brought into the microgrids study considering the intermittence, randomness characteristics of renewable energies. As a result, the power generations of distributed generators fluctuate frequently. Furthermore, it is difficult to obtain the parameters of microgrids accurately. Thus, the study on small signal stability of microgrids is especially important. This paper presents a review of exiting small signal stability methods for microgrids. Besides, a new approach based on Singular Entropy and Matrix Pencil is proposed. Meanwhile, its validity and effectiveness are confirmed by some examples compared with Prony algorithm. Then, the proposed method is also applied into a microgrid with an improved droop control strategy. Finally, a framework based on the proposed method for small signal stability, warning and emergency control online in microgrids is available. © 2011 Elsevier Ltd. All rights reserved.

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


Zeng Z.,Zhejiang University | Yang H.,Zhejiang University | Zhao R.,Zhejiang University | Cheng C.,Zhejiang University
Renewable and Sustainable Energy Reviews | Year: 2013

Grid-connected inverters are key components of distributed generation systems (DGSs) and micro-grids (MGs), because they are effective interfaces for renewable and sustainable distributed energy resources (DERs). Recently, multi-functional grid-connected inverters (MFGCIs) have attracted more and more attention for their benefits on auxiliary services on power quality enhancement in DGSs and MGs. These kinds of converters can not only achieve the power generation of DERs, but also can perform as power quality conditioners at their grid-connected points. It should be noted that these functionalities are optimally organized in the same device, which can significantly enhance the cost-effective feature of the grid-connected inverter, as well as can decrease the investment and bulk compared with multiple devices with independent functionalities. MFGCIs are especially suitable for DGSs and MGs application due to their good performances and benefits. Topologies and control strategies of MFGCIs are comprehensively reviewed in this paper. Additionally, detailed explanation, comparison, and discussion on MFGCIs are achieved. Furthermore, some future research fields on MFGCIs are well summarized. © 2013 Elsevier Ltd.

Document Keywords (matching the query): energy resources, distributed generation system.


Gu Y.,Zhejiang University | Xiang X.,Zhejiang University | Li W.,Zhejiang University | He X.,Zhejiang University
IEEE Transactions on Power Electronics | Year: 2014

A mode-adaptive decentralized control strategy is proposed for the power management of a dc microgrid with multiple renewable distributed generators and energy storage systems. In the presented solution, the dc bus voltage signal is used not only to enable power sharing among different sources, but also to designate microgrid operation modes and facilitate seamless mode transitions. With this mode-adaptive operation mechanism, a greater control freedom can be achieved than the conventional dc voltage droop control scheme. More importantly, this approach features fully self-disciplined regulation of distributed converters without an extra control center or communication link. Therefore, both reliability and flexibility can be enhanced. Meanwhile, a novel mode definition criterion is also provided to highlight the special characteristics of the dc microgrid which is different from an ac one. Three typical operation conditions are summarized according to which type of sources are dominating the power balance. Finally, the effectiveness of the proposed technique is verified experimentally based on a composite dc microgrid test system. © 2013 IEEE.

Document Keywords (matching the query): distributed generators, energy storage systems, distributed power generation.


Li W.,Zhejiang University | Xiang X.,Zhejiang University | Li C.,Zhejiang University | He X.,Zhejiang University
IEEE Transactions on Power Electronics | Year: 2013

In this paper, the concept of built-in transformer voltage doubler cell is derived to generate an improved interleaved high step-up converter for distributed photovoltaic generation applications. The proposed built-in transformer voltage doubler cell is composed of three transformer windings, two voltage doubler diodes, and two voltage doubler capacitors. The voltage doubler capacitors are charged and discharged alternatively to double the voltage gain. The switch duty cycle and the transformer turns ratio can be employed as two controllable freedoms to lift the voltage ratio flexibly. The power device voltage stress can also be reduced to improve the circuit performance. Furthermore, the active clamp scheme is adopted to recycle the leakage energy, absorb the switch turn-off voltage spikes, and achieve zero-voltage switching (ZVS) operation for all active switches. Meanwhile, the diode reverserecovery problem is alleviated by the leakage inductance of the built-in transformer. All these factors benefit the circuit performance improvements in the high step-up and large current applications. Finally, a 1-kW prototype with 40-380 V conversion is built and tested to demonstrate the effectiveness of the proposed converter. © 2012 IEEE.

Document Keywords (matching the query): pv generation, leakage energies, photovoltaic generation.


Yang Q.,Zhejiang University | Laurenson D.I.,University of Edinburgh | Barria J.A.,Imperial College London
IEEE Transactions on Smart Grid | Year: 2012

The passive nature of power distribution networks has been changing to an active one in recent years as the number of small-scale Distributed Generators (DGs) connected to them rises. The consensus of recent research is that current slow central network control based upon Supervisory Control and Data Acquisition (SCADA) systems is no longer sufficient and Distributed Network Operators (DNOs) wish to adopt novel management mechanisms coupled with advanced communication infrastructures to meet the emerging control challenges. In this paper, we address this issue from the communication perspective by exploiting the effectiveness of using a Low Earth Orbit (LEO) satellite network as the key component of the underlying communication infrastructure to support a recently suggested active network management solution. The key factors that would affect the communication performance over satellite links are discussed and an analytical LEO network model is presented. The delivery performance of several major data services for supporting the management solution is evaluated against a wide range of satellite link delay and loss conditions under both normal and emergency traffic scenarios through extensive simulation experiments. Our investigation demonstrates encouraging results which suggests that a LEO network can be a viable communication solution for managing the next-generation power energy networks. © 2010-2012 IEEE.

Document Keywords (matching the query): next generation networks, power energy, distributed network operators, distributed power generation, distributed generators.


Zhu K.,Zhejiang University | Jiang D.,Zhejiang University | Hu P.,Zhejiang University
Dianwang Jishu/Power System Technology | Year: 2012

A new type of dc distribution network containing electric vehicle (EV) charge station is proposed. Based on physical features of three distributed generation units, namely photovoltaic (PV) cell, solid fuel cell and wind power generator, the grid-connected models of them are built, and simple and reliable grid-connection mode is designed, thus the cost for grid-connection of distributed generation (DG) is evidently reduced. The EV charge station, which is taken as a balanced node in DC distribution network, is connected to power grid, and the energy interchange is implemented by converter devices and storage battery in charge station, and the cost for the investment and construction of energy storage devices can be saved. A three-layer control method for such a new type of DC distribution network is put forward. The feasibility of the proposed system is verified by results of PSCAD/EMTDC-based simulation, and it is also shown that the proposed control method can ensure reliable power supply for the charge system and uttermost utilization of DG, and it is convenient for energy interaction and implementation of optimal economic dispatching.

Document Keywords (matching the query): energy interchange, distributed generation units, energy interactions, distributed power generation, distributed generation.

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