This paper proposes a high-powercontrollable current quality disturbance generator, which is composed of multiplex cascade H bridge modules, and simulates current quality problems, such as positive and negative curre...
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This paper proposes a high-powercontrollable current quality disturbance generator, which is composed of multiplex cascade H bridge modules, and simulates current quality problems, such as positive and negative current distrubance, current fluctuation, harmonic current and so on. The device adopts a topology with decoupling fundamental and harmonic current. A power module parallel-connected on the fundamental connection reactance outputs harmonic current, while cascade fundamental power modules generate fundamental and low order harmonic current, which realizes decoupling control of fundamental and harmonic current. This paper proposes the control strategies of all types of current disturbances, and the Ether Cat-based controller. Finally, a 10 k V/1MVA controllable current quality disturbance generator has been created. The experiment result proves that the proposed main circuit topology, control strategy and Ether Cat-based controller are feasible and efficient. The emergence of this device creates a fundamental platform for measurement, analysis, evaluation and control of current quality in grid.
Frequency stability refers to the ability of a powersystem to maintain steady frequency following a severe system upset resulting in a significant imbalance between generation and load. The rate of frequency change (...
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Frequency stability refers to the ability of a powersystem to maintain steady frequency following a severe system upset resulting in a significant imbalance between generation and load. The rate of frequency change (df/dt) is an instantaneous indicator of power deficiency and can incipient recognition of power imbalance. The new method presented in this paper assumes the application of the WAMS as a base for their successful implementation. The adaptive scheme aims to extract the relevant powersystem parameters from on-line measurements. Therefore, the scheme can adapt its sensitivity to the current operating conditions, eliminating the need for many assumptions that have to make when tuning the conventional local scheme. In the predictive step, this model is used to estimate a frequency trajectory following a disturbance. The proposed scheme uses the local frequency rate information to adapt the load shedding behavior to the size and location of the experienced disturbance. Based on this prediction it can be determined whether emergency UFLS control actions are necessary.
This paper proposes a high-powercontrollable voltage quality disturbance generator, which is composed of multiplex cascade H bridge modules, and simulates many types of voltage quality problems, such as voltage swell...
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This paper proposes a high-powercontrollable voltage quality disturbance generator, which is composed of multiplex cascade H bridge modules, and simulates many types of voltage quality problems, such as voltage swell and sag, fluctuation and flicker and so on. One side of the device connects the powersystem with cascade H bridge to improve voltage level. The other side connects the system directly to aviod the problems caused by series transformer, such as additional phase shifting and voltage drop. Cascade inverter H bridge modules and PWM rectifier H bridge modules are all controlled by triangular carrier phase shifting to increase the equivalent switching frequency of inverter to simplify the control. Finally, a 10 k V/2MVA controllable voltage quality disturbance generator has been created. The experiment result proves that the proposed main circuit topology, control strategy and Ether Cat-based controller are feasible and efficient.
Principal components analysis uses a mathematical procedure that transforms a set of correlated response variables into a new set of uncorrelated variables. The few principal components contain almost all of the infor...
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In this paper, a novel fault location method based on Principal Component Analysis (PCA) is proposed, in which synchronized information data are utilized provided by the WAMS/PMU measurement system. PCA method is an e...
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ISBN:
(纸本)9781457710001
In this paper, a novel fault location method based on Principal Component Analysis (PCA) is proposed, in which synchronized information data are utilized provided by the WAMS/PMU measurement system. PCA method is an efficient mathematic tool to reduce dimensions. Therefore, the state matrix, consisting of raw synchrophasor information versus multi-points and various times, is compressed effectively. By the remained key features, the corresponding principal component scores could be obtained. The simulation results have shown that, according to these scores, the fault component can be confirmed exactly. A great number of simulation trials have fully proved that the results of principal component analysis are accurate and reliable.
After taking the element of adjacent matrix as the function of the state of edges in the network structure, the representation of the element in corresponding adjoint matrix has been given an in-depth analysis. With t...
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ISBN:
(纸本)9781457710001
After taking the element of adjacent matrix as the function of the state of edges in the network structure, the representation of the element in corresponding adjoint matrix has been given an in-depth analysis. With the use of simplifying method on each element in adjoint matrix, the complete connected matrix could be formed equally with the each element as the set of connected routes. Based on the above analysis and processing, the new connected routes finding algorithm is established, which is a systematic method and suitable for all kinds of network connections. Finally, the successful application to substation configuration has validated the efficiency of the novel algorithm in powersystem topology analysis, in which the connected routes can be formed in off-line way and be used for topology analysis in on-line way. Therefore, the aim to reduce topology analysis time could be achieved.
The transient mathematical models of two VSC-HVDC systems which are supplying active and passive networks respectively are developed in d-q synchronous reference frames. All the controllers were designed and realized ...
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The transient mathematical models of two VSC-HVDC systems which are supplying active and passive networks respectively are developed in d-q synchronous reference frames. All the controllers were designed and realized current decoupled controls by applying PI (Proportional-Integral) regulators. A 2-Level VSC-HVDC supplying active network with fixed DC voltage control in rectifier side and fixed active powercontrol in inverter side was modeled, then a 3-Level VSC-HVDC supplying passive network with fixed DC voltage control in rectifier side and fixed AC voltage control in inverter side was modeled thereafter, then their operational characteristics were tested and compared by simulations in PSCAD/EMTDC, which verified the effectiveness and stability of the designed controllers and validated great potentiality in future VSC-HVDC projects.
Real-time digital simulation has been widely used in powersystem analysis, which is becoming a very important tool to system planning, feasibility studies, and new equipment design, and the accuracy of real-time digi...
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Real-time digital simulation has been widely used in powersystem analysis, which is becoming a very important tool to system planning, feasibility studies, and new equipment design, and the accuracy of real-time digital simulation has great effects on the security and economic efficiency of powersystem operation. In this paper, residual similarity is calculated by average percentage error, and shape similarity is calculated by coefficient method. Accuracy assessment method of real-time digital powersystem simulation is proposed concerning the two similarity indexes from the static and dynamic perspective. During the assessment of similarity of two curves, both the residual error between the two curves and the similar extent of variation trend of the curves are considered, and the assessment result is helpful to model modification. Analysis based on measurement data of test occurring in a certain ultra HVDC transmission powersystem of China and the simulation results on RTDS is presented, which proves the validity of this method.
Due to the energy crisis and global warming problems, most of the countries place more and more emphasis on the development of distributed generation (DG) using renewable energy. In China the installed capacity of dis...
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Due to the energy crisis and global warming problems, most of the countries place more and more emphasis on the development of distributed generation (DG) using renewable energy. In China the installed capacity of distributed generators is rising, from isolated micro-grid system to grid connected system. With the increasing penetration of distributed generation, especially for the converter interfaced DG, their impacts on the protection of distribution system cannot be neglected. In this paper, the models of two types of DG, i.e. converter based DFIG and inverter interfaced DG, are reviewed. Moreover, the fault analysis of the two types of DG is investigated systematically and the impacts on protections are analyzed as well.
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