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Hangzhou, China

Tu Q.,Zhejiang University | Xu Z.,Zhejiang University | Zheng X.,Zhejiang University | Zhang J.,Hangzhou Electric Power
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2011

Modular multilevel converter based HVDC (MMC-HVDC) is a new generation VSC-HVDC topology invented by Siemens. The problem of voltage balancing among the submodules (SM) is difficult to solve. The traditional method, which uses the sorting results of the SM capacitor voltages and fires the IGBTs directly, leads to relatively higher power losses. This paper proposes an improved voltage balancing control method, which reduces the switching operation significantly and the switching losses of the converter decreases consequently. The model of MMC-HVDC with 20 SMs is realized by PSCAD/EMTDC, and the traditional and improved voltage balancing control methods are compared. The simulation results demonstrate that the model is reasonable and the improved method is effective. Source

Guo C.X.,Zhejiang University | Bai Y.H.,Zhejiang University | Zheng X.,Hangzhou Electric Power | Zhan J.P.,Zhejiang University | Wu Q.H.,University of Liverpool
International Journal of Electrical Power and Energy Systems | Year: 2012

Traditional economic dispatch focuses mainly on minimizing the total operation cost of the power system. With the appearance of energy crisis and environmental pollution becoming a public issue, environmental effect of generator should be taken into consideration through the dispatch process. In this paper a multi-objective dispatch problem considering the integration of wind power is solved whose objectives include the generation cost, the reserve capacity and the environmental emission. To compromise different objectives, a coordination degree combined with a satisfaction degree are introduced in order to transform the multi-objective dispatch problem into a single-objective one, i.e., the optimal generation dispatch (OGD) model. Then the OGD is solved by a particle swarm optimization algorithm on an IEEE 30-bus system, with wind power generation and coal-fired generation embedded. The simulation results show that better results in terms of all the three objectives can be obtained from the OGD model, in comparison with two other multi-objective dispatch models. The simulation results also show that the integration of wind power will cause the increase of both the generation cost and the reserve capacity but will decrease the environmental emission. © 2012 Elsevier Ltd. All rights reserved. Source

Zhu T.,China Southern Power Grid Co. | Wang C.,Hangzhou Electric Power
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

A complicated DC line fault of high voltage direct current (HVDC) is analyzed. During this DC line fault, the continuous lightning strikes resulted to action of several protections such as: DC line over-voltage protection, valve group differential protection, AC/DC conductor contact protection, bridge differential protection and 50 Hz protection, etc. In accordance with protection function principle of DC control concerned and fault records, a detailed analysis on the fault process is carried out. Furthermore, the improving suggestions such as: study on reason and influence of DC line over-voltage, attach importance to the coordination of thyristor valve and its control system with the DC protection, properly improve the logic of the open HSNBS, etc are put forward. © 2011 State Grid Electric Power Research Institute Press. Source

Hong-juan H.,North China Electrical Power University | Zhen-yue Y.,North China Electrical Power University | Zhen-yue Y.,Hangzhou Electric Power | Yong-ping Y.,North China Electrical Power University | And 3 more authors.
Applied Energy | Year: 2013

Integrating solar energy with a coal-fired power plant or other power systems has been proved to be an efficient way to utilize solar energy for power generation. Solar aided feedwater heating of a coal-fired power generation (SAFHCPG) system, which is mainly discussed in this paper, is chosen as an option for its easy operation and flexible control nature.The performance of a SAFHCPG system at design point is analyzed under various load conditions in the paper. As the results show in Table 4, the lower load of coal-fired unit that solar aid, the lower solar-to-electric efficiency will be. For a SAFHCPG system, its performance is influenced by the solar radiation intensity and the electrical load demand on the grid side. The correlation between the annual performance of a SAFHCPG plant and the two key factors is discussed and then the optimal aperture area of solar field is derived. The result shows that, for the case studied the optimal aperture area of solar field and the lowest LEC (Levelized Electricity Costs) are: 115395m2 and 0.472/kWh in a typical year; 138945m2 and 1.010/kWh in an extremely low radiation year; 91845m2 and 0.426/kWh in an extremely high radiation year respectively. © 2013. Source

Wang P.-C.,Hangzhou Electric Power
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

Existing disconnector auxiliary contact and its introduction are not very reliable, which will influence that the bus differential protection would not protect the fault bus. Through the inductive analysis, it proposes two improved kinds of hardware and software solutions, and discusses their influences on widely used bus differential protection. Now combining with a case of auxiliary switch contact status error happened in a substation, this paper discusses the influences of disconnector auxiliary contact status error on bus differential protection and proposes the solutions against it. Source

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