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Ji Li

Bio: Ji Li is an academic researcher from Tianjin University of Technology. The author has contributed to research in topics: Saddle-node bifurcation & AC power. The author has an hindex of 4, co-authored 26 publications receiving 112 citations.

Papers
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Proceedings ArticleDOI
Youjie Ma1, Haishan Yang1, Xuesong Zhou1, Ji Li1, Hulong Wen1 
13 Nov 2009
TL;DR: In this paper, the Jensen wake model was used to estimate the wind turbine output power under the four-component wind speed model, and the output power was researched based on the Jensen Wake model, which combined of the dynamic wind turbine model; anglicizing with the distribution of wind power from the theoretical, optimization method that named quadratic interpolation.
Abstract: Under the four-component wind speed model, the wind turbine output power was researched based on the Jensen wake model, which combined of the dynamic wind turbine model; anglicizing with the distribution of wind power from the theoretical, optimization method that named quadratic interpolation was used, and the optimization tool of Matlab\simulink verified that the correct conclusion has a certain rationality. Rational arrangement of wind turbine in order to minimize wake effects, so that the output of wind power can be improved, the study of optimal operation of wind farms and planning issues related to be a certain value.

35 citations

Patent
16 Feb 2011
TL;DR: In this article, a singlechip-based induction motor variable frequency speed regulation control system is presented, which consists of a main circuit, an auxiliary power circuit, inverter circuit, control part, over-current protection circuit, a rotation speed detection circuit and other peripheral circuits.
Abstract: The invention discloses a singlechip-based induction motor variable frequency speed regulation control system. The system comprises a main circuit, an auxiliary power circuit, an inverter circuit, a control part, an over-current protection circuit, a rotation speed detection circuit and other peripheral circuits. A 16-bit high-performance signal controller dsPIC30F4011 which is produced by the Microchip Company is used as a control core by the system to perform speed regulation based on vector control motor excitation. A digital signal controller dsPIC30F4011 of the America Microchip Technology Company is used as a chip special for motor control, a digital signal processor (DSP) inner core is embedded, and the chip has quick data processing capacity and is provided with abundant input and output equipment and interface circuits; an intelligent power module (IPM) IRAMSIOUP 60A of the IR Company is an inverter switching device, so that the variable frequency speed regulation control system of an asynchronous motor is constructed; and the system has the characteristics that the system is simple to drive and easy to realize.

33 citations

Patent
28 Apr 2010
TL;DR: In this paper, an integrated rotor excitation control system of double-fed motor based on self interference resistance is presented. But the system does not need to be changed and the control performance is not influenced by amplitude limit.
Abstract: The invention discloses a w ind and power integrated rotor excitation control system of double-fed motor based on self interference resistance is composed of a d axis current control unit of an inner ring rotor, a q axis current control unit of the inner ring rotor and a voltage control unit of an outer ring stator. The invention has the following advantages: (1) the structure is simple and the project is easy to realize; (2) parameters do not need to be changed; (3) the control performance is not influenced because of amplitude limit; (4) the robustness is stronger; (5) effective information of the system can be maximally used and the dynamic performance of the system is improved; and (6) the anti-interference capacity is strong.

5 citations

Patent
16 Feb 2011
TL;DR: In this paper, a real-time simulation system using a neural network and a digital signal processor (DSP) coprocessor (SEED-C30PS) is presented.
Abstract: The invention relates to a wind power system modeling and DSP (Digital Signal Processor) realizing method based on a neural network, comprising the following steps of: determining input and output signals by analyzing working mechanisms of a wind power system and the neural network, wherein the input signal includes wind speed and a propeller pitch angle, the output signal includes power, wind wheel rotating speed and a wind wheel torque The invention can achieve any training accuracy to determine the weight value of each layer by combining the BP neural network with the wind power system, establishing a BP neural network model and setting a hidden layer number to be large enough, thereby well fitting the property of a modeling object; in order to realize the application possibility, the invention designs a neural network real-time simulation system realized by adopting DSP as a neural network computation coprocessor (SEED-C30PS); in addition, the invention realizes the BP neural network used for the parameters of the wind power system on a DSP system according to fast arithmetic capability determined by the specific hardware structure of a DSP chip, thereby enhancing the arithmetic speed of the system and enabling the system to meet the requirements for instantaneity

4 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors compared different far wake models and found that the Jensen's far wake model is a good choice to solve the wind farm layout problem due to its simplicity and relatively high degree of accuracy.
Abstract: The layout scheme of wind farms is a challenging job having many design objectives and constraints due to the multiple wake phenomenon. Wake effect calculation is one of the significant problems in the wind farms and needs to be modeled to decrease the power loss due to near and far wake effect. This paper reviews the wake models in general and far wake models in particular. The comparison of different far wake models shows that the Jensen׳s far wake model is a good choice to solve the wind farm layout problem due to its simplicity and relatively high degree of accuracy. This research also focuses on the studies carried out on wind farm layout optimization problem and the current state of the art of fitness functions used for the optimization of wind farms using Jensen׳s wake model. It is found that there is a need of more optimization techniques to be applied to solve the layout problem. In addition, future advancements have been identified for better positioning of wind turbines in larger wind farms.

217 citations

Journal ArticleDOI
TL;DR: In this paper, a particle swarm optimization (PSO) algorithm was used to find the optimized layout, which minimizes the levelized production cost (LPC) objective function.
Abstract: With the increasing size of wind farms, the impact of the wake effect on wind farm energy yields become more and more evident. The arrangement of locations of the wind turbines (WTs) will influence the capital investment and contribute to the wake losses, which incur the reduction of energy production. As a consequence, the optimized placement of the WTs may be done by considering the wake effect as well as the components cost within the wind farm. In this paper, a mathematical model which includes the variation of both wind direction and wake deficit is proposed. The problem is formulated by using levelized production cost (LPC) as the objective function. The optimization procedure is performed by a particle swarm optimization (PSO) algorithm with the purpose of maximizing the energy yields while minimizing the total investment. The simulation results indicate that the proposed method is effective to find the optimized layout, which minimizes the LPC. The optimization procedure is applicable for optimized placement of WTs within wind farms and extendible for different wind conditions and capacity of wind farms.

124 citations

Patent
26 Feb 2014
TL;DR: In this paper, a system for hydraulically fracturing an underground formation in an oil or gas well to extract oil and gas from the formation is described, the system includes a plurality of pumps powered by electric induction motors and fluidly connected to the well, the pumps configured to pump fluid into the wellbore at high pressure so that the fluid passes from the well-bore into the, and fractures the formation.
Abstract: A system for hydraulically fracturing an underground formation in an oil or gas well to extract oil or gas from the formation, the oil or gas well having a wellbore that permits passage of fluid from the wellbore into the formation. The system includes a plurality of pumps powered by electric induction motors and fluidly connected to the well, the pumps configured to pump fluid into the wellbore at high pressure so that the fluid passes from the wellbore into the, and fractures the formation. The system can also include a plurality of natural gas powered generators electrically connected to the plurality of pumps to provide electrical power to the pumps.

78 citations

Patent
15 Oct 2015
TL;DR: In this paper, a centralized monitoring and control of a hydraulic fracturing operation is described, which includes an electric powered fracturing fleet and a centralized control unit coupled to the electric powered hydraulic fracturing fleet.
Abstract: A system and method are disclosed for centralized monitoring and control of a hydraulic fracturing operation. The system includes an electric powered fracturing fleet and a centralized control unit coupled to the electric powered fracturing fleet. The electric powered fracturing fleet can include a combination of one or more of: electric powered pumps, turbine generators, blenders, sand silos, chemical storage units, conveyor belts, manifold trailers, hydration units, variable frequency drives, switchgear, transformers, and compressors. The centralized control unit can be configured to monitor and/or control one or more operating characteristics of the electric powered fracturing fleet.

71 citations

Journal ArticleDOI
TL;DR: A review of the state-of-the-art researches related to the wind farm layout optimization as well as electrical system design including cable connection scheme optimization is presented in this paper, where the most significant factors that should be considered in the offshore wind farm optimization work is highlighted after reviewing the latest works, and the future needs have been specified.
Abstract: There is more wind with less turbulence offshore compared with an onshore case, which drives the development of the offshore wind farm worldwide. Since a huge amount of money is required for constructing an offshore wind farm, many types of research have been done on the optimization of the offshore wind farm with the purpose of either minimizing the cost of energy or maximizing the total energy production. There are several factors that have an impact on the performance of the wind farm, mainly energy production of wind farm which is highly decided by the wind condition of construction area and micro-siting of wind turbines (WTs), as well as initial investment which is influenced by both the placement of WTs and the electrical system design, especially the scheme of cable connection layout. In this paper, a review of the state-of-art researches related to the wind farm layout optimization as well as electrical system design including cable connection scheme optimization is presented. The most significant factors that should be considered in the offshore wind farm optimization work is highlighted after reviewing the latest works, and the future needs have been specified.

66 citations