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Ye L.,China Agricultural University | Sun H.B.,Sichuan Electric Power Corporation | Song X.R.,China Electric Power Research Institute | Li L.C.,China Agricultural University
Renewable Energy | Year: 2012

Microgrids are LV or MV electric networks which utilize various distributed generators (DG) to serve local loads. In this paper, dynamic models of the main distributed generators including photovoltaic (PV) cell, wind turbine, hydro turbine as well as the equivalent power electronic interfaces, battery unit of PV and excitation system of hydro turbine have been made in ElectroMagnetic Transient Program/Alternative Transient Program (EMTP/ATP) software package. Control strategies based on active power/frequency and reactive power/voltage droops for the power control of the inverters have been also developed. Case studies have been carried out in a distribution network to investigate the dynamic behavior of the micro-sources in both steady state and fault scenarios. Simulation results verify the feasibility of the proposed models. © 2011 Elsevier Ltd.

Shu Z.,Southwest Jiaotong University | He X.,Emerson Electric | Wang Z.,Emerson Electric | Qiu D.,Sichuan Electric Power Corporation | Jing Y.,Southwest Jiaotong University
IEEE Transactions on Power Electronics | Year: 2013

An auxiliary capacitor-based balancing approach is adopted in this paper to equalize the dc-link capacitor voltages of a diode-clamped multilevel converter (DCMC). Four balancing circuits, including the generalized, one-level-capacitor, one-capacitor, and simplified one-capacitor-based configurations are discussed for a five-level DCMC system. These configurations are different in connection of the auxiliary circuits and numbers of the capacitors and switches, but they work on the same principle called ping-pong operation by utilizing the auxiliary capacitor as an equalizer between the capacitors of different voltages. The unbalance phenomenon, ping-pong principle, circuit configurations, and their switching schemes are analyzed, respectively. The superiorities of the proposed approach include balancing operation regardless of load power factor and modulation index, control simplicity, and independence from main circuits when compared to the traditional approaches. Simulations and experimental results verified the performances using the proposed balancing circuits and control strategies. © 1986-2012 IEEE.

Chen L.,Sichuan Electric Power Corporation
Advanced Materials Research | Year: 2014

To reduce the interference on communication equipments caused by transient electromagnetic field of switching operation, the shields of cables are connected to grounding grid on both sides in the substations grounding designs. However, when the substation is stroke by lightning or shorted, the huge potential difference called diverting potential difference between the cable core and the shield is generated, which can easily destroy insulation of cables, even producing electrical tree or dielectric breakdown in insulation material. Moreover, the large current flowing through the shield of cables will cause personnel accidents and equipment damages. In this paper, the electric model of cables is established using grounding grid simulation software-CEDGS. The way diverting potential difference changes influenced by grounding grids, soil and other parameters is analyzed. Measures to reduce diverting potential difference are proposed for providing a theoretical basis of construction in practice. © (2014) Trans Tech Publications, Switzerland.

Guo L.,Sichuan Electric Power Corporation | Lu F.-P.,University of Sichuan
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

In respect to the defect that the location result of the present travelling wave fault location algorithm for T-connection transmission line is easily affected by travelling wave velocity, this paper proposes a new method for the fault location on T-connection transmission lines, which is based on the principle that the traveling wave velocity is equal on the same condition. Only line parameters and the arriving time of initial fault current transient traveling waves to line three-side are needed in the method, where there is not a dead zone when fault occurs nearby the T-connection node, and the influence of the wave velocity on fault branch judgement and location accuracy on part condition is also excluded. The results of simulation show that the proposed method has simple computation, higher accuracy and can meet the requirement of fault location.

Chen D.,Sichuan Electric Power Corporation
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

By theoretical analysis, the calculation model of DC current distribution of AC power grid is built to explore the mechanism of DC current distribution in AC power grid. The forecast and analysis of Jinping-Sunan ±800 kV UHVDC 4950A earth-return current distribution rule in Sichuan power grid as well as substations' taking risks of DC magnetic biasing is carried out in line with the 2014 program. Computation results show that the area of infection is mainly within the radius of 120 km around DC grounding electrode. In the end, the effect of Jinping-Sunan ±800 kV UHVDC on the UHV substation to be built as well as its mitigation measurement is particularly discussed. Evaluation results show that these problems will not be serious.

Huang J.-P.,Sichuan Electric Power Corporation
Proceedings - 2013 2nd International Symposium on Instrumentation and Measurement, Sensor Network and Automation, IMSNA 2013 | Year: 2013

The principle of single phase three-level PWM rectifier is discussed. Based on the definition of αβ variable, a mathematic model of the adopted rectifier on the dq reference frame is set up. Based on linear decoupled theory, a decoupled current control strategy is proposed which declines significantly complexity of the control system and has good control characteristics. Computer simulation and experiment results demonstrate that this rectifier under decoupled current control has higher power factor and better dynamic performance, which confirms the effectiveness of the improved control strategy. © 2013 IEEE.

Xu Y.,Sichuan Electric Power Corporation
Applied Mechanics and Materials | Year: 2013

The time resolved partial discharge (TRPD) signals collected by Ultra High Frequency (UHF) sensors of transformer contain important informations of the properties of faults. Wealth of information can be utilized for fault identification by different signal analyzing techniques, such as time domain analysis, frequency domain analysis and the wavelet analysis. An integrated characteristic information fusion system based on the Platt posterior probability model and support vector machine (SVM) 'one-against-one' method is proposed. From the recognition result of the four typical insulation defects, the recognition system shows strong advantages in accuracy and reliability. © (2013) Trans Tech Publications, Switzerland.

Chen G.,University of Sichuan | Qiu X.,University of Sichuan | Lin W.,Sichuan Electric Power Corporation
Dianwang Jishu/Power System Technology | Year: 2012

Energy storage system is an important component of microgrid and it greatly impacts the stability, security and economic operation of microgrid. Taking a microgrid containing energy storage system composed of vanadium redox flow battery (VRB) as research object, a multi-objective load distribution optimization model of microgrid with energy storage system composed of vanadium redox flow battery (VRB) is built. The economic benefit bought to microgrid by VRB is analyzed and researched, meanwhile the influences of the factors such as operating modes, control strategy and the weights of optimization objectives on load distribution optimization of microgrid are researched too, thus the effectiveness of the built model is verified.

Ma W.-D.,Sichuan Electric Power Corporation
Gaoya Dianqi/High Voltage Apparatus | Year: 2012

According to the basic principle of maximum power point tracking (MPPT) and the characteristics of common control system for wind power conversion, a three-point comparison method based on duty cycle perturbation is presented. In the practical system implementation, the MPPT methods are integrated in the digital signal processor (DSP) TMS320C6711 to adjust the duty ratios of DC/DC chopper converter to control the generator working with maximum power output. Taking a 1.5 kW wind turbine for example, the experiment results from the TMS320C6711 based platform show that the present three-point comparison method can track the maximum power point more effectively and rapidly, compared with the conventional current-type perturbation & observation (P&O) method.

Han Y.,University of Sichuan | Li H.,Sichuan Electric Power Corporation
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2012

A bus load forecasting model based on wavelet transform and SVM(Support Vector Machine) is proposed to improve its accuracy, which applies the wavelet transform to decompose the target bus load sequence into the components of different frequencies, analyzes their characteristics to build SVM model for each component, forecasts separately the load of each component, and reconstructs them to obtain the final forecast. The loads of 15 buses in an area are studied and the average daily bus load accuracy is used as the index for comparison. Compared with the model only based on SVM, 66.8% of point forecasting accuracies, i. e. 962 points, are improved, and the overall forecasting accuracy increases from 93.5% to 95.1%.

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