The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The tremendous usage of power electronic devices in power system makes the harmonic pollution can't be ignored any more. Harmonic contents in power system is one of the indexes to evaluate the power quality. Alternative Transients Program (ATP) has obvious advantages in transient calculation. While it is difficult to carry out the electromagnetic transient calculation of actual power grid due to its...
This paper proposes a novel modular multilevel DC/DC converter(MMDDC) used in super capacitor energy storage system(ESS). Unlike the conventional MMDDC, this converter has an ability to overcome the problem associated with over-current in charge mode. Along with that, it also possesses advantage of convenience in pre-charging super capacitors(SCs) from DC link without additional charging circuits...
The shortage of energy and the deterioration of the environment have become increasingly prominent. A large number of distributed generation access to distribution network, network structure changes. Because of the fast response characteristic of the inverter interfaced distribution generation (IIDG), the instantaneous current protection of distribution network appears to be wrong or refused to move...
The location and sizing of distributed generation (DG) have great influence on distribution network. Issues on locating and sizing of dispersed wind generation(DWG) are discussed in this paper. The network loss index and voltage stability index are analyzed as objective function in detail to reduce the network loss and improve voltage quality effectively. Sensitivity analysis method is first used...
Natural frequency is formed because that fault traveling wave reflects between fault point and the line end. And it has definite mathematical relationship with fault distance. Characteristics difference of natural frequency values under different fault types is analyzed in this paper, including dc transmission line faults, VSC converter faults, and ac system faults. And protection criterion is formed...
Environmental pollution and energy shortage have resulted in a recent strong demand for distribution networks to accept renewable clean energy. As an important part of distributed generations, DWP wind power (DWP) with its clean and flexible characteristics has been an important focus of domestic and foreign entities. In this paper, high penetration optimal operation model for DWP wind farm (DWF)...
A DC distribution line protection method based on parameter identification is proposed. The parameter equation in the conditions of monopolar grounding fault and pole-to-pole fault is deduced by analyzing DC distribution line faults, the protection scheme for DC distribution line is researched based on the principle of parameter identification. The protection scheme utilizes the voltage and current...
Due to the numbers of transformer, the closing angle and other reasons, the inrush current performed intricately, which usually made the protection miss operation. Therefore, reliability and stability in protection of transformer is important task in distribution system. In this paper, an efficient method for detection of inrush current is presented, which is based on the attenuation factor of current...
An analytical expression of the stator current of DFIG and the flux of stator and rotor is obtained, by analyzing the transient model of DFIG (Doubly-fed Induction Generator). And the analytical expression of the active power of DFIG and the rotor reaction flux is obtained by vector analysis of stator current and rotor flux. Then, this paper infers the analytical expression of the active power output...
The optimization schedule strategy of the active distribution system (ADS) is the core technology required to actively manage distributed energy resources (DERs). This paper establishes an optimal scheduling model for the ADS, whose blurring purposes are voltage quality improvement and operation cost reduction under control variables of different kinds of distributed generators (DGs). In addition,...
The high permeability integration of the distributed wind power accessed to the traditional network, topological structure has changed from radialized to active. The amplitude and phase of the fault current are changed greatly and it is difficult for the traditional three-current protection to adapt this. By analyzed the fault transient characteristics of the doubly-fed induction wind generator (DFIG),...
Ferroresonance overvoltage that is caused by saturation in electromagnetic type voltage transformers occurs frequently. In order to avoid interference from ferroresonance overvoltage in the safe operation of a power system, it is a to study a reliable and stable resonance elimination measure. Firstly, different types of ferromagnetic resonances are obtained with the different ratio of capacitive reactance...
Developments in power capacity have made arc grounding overvoltage increasingly prominent. This paper proposes a new method for determining current-voltage (I-V) characteristics of ZnO nonlinear resistance on a new grounding mode, by analyzing the power system through the symmetrical component method, considering system capacities, operation mode, and other characteristics. Then, the I-V characteristics...
In frequency domain, there is a certain mathematical relationship between the natural frequency and the fault distance. But model mixing is still the problem haven't been solved well yet, it brings difficulty in gaining the natural frequency. A combined fault location algorithm for HVDC transmission line based on natural frequency is proposed in this paper, in which time domain and the frequency domain...
In order to improve the accuracy of the wind power forecasting, aiming at the high volatility and weak Gaussion distribution feature of the wind power output, this paper proposes a new criterion — Maximum Correntropy Criterion (MCC) to guide the parameter optimization process of least square support vector machine (LSSVM). In the model, firstly, the measured data of wind farm is filtered and normalized...
There are two primary troubles having effect on reliability in tradition traveling-wave distance protection schemes. One is reflection wave identification for single-ended traveling-wave protection (A-type), and another is time synchronization for two-ended traveling-wave protection (D type). This paper proposes a novel protection for transmission line unsymmetrical grounded faults, which only needs...
The conducted common-mode EMI of PWM motor drive system has enhanced systematic radiated interference because its circulating path includes the earth. At the same time it also brings conducted interference to other electrical system in the form of interference current and brings negative effects. In order to predict the conducted common-mode EMI, based on deep research of the interference source and...
This paper presents a high-speed directional relay for EHV transmission line. The basic principle of the directional relay is based on comparing high-frequency component energy of directional traveling waves of each bus outgoing line. The relay comparison scheme is designed with intrinsic mode function (IMF) from empirical mode decomposition. The IMF is used to extract transient features from fault-generated...
The development of distributed generation (DG) has a great influence on the traditional power systems and received considerable attention in recent years. After interconnected DG, the voltage maybe to rise along the feeder, and has serious potential impacts on distribution system. This paper introduction the algorithm based on distributed slack buses model through adjusted Newton-Raphon, the participated...
Among the traditional schemes of current differential protection for power transformer, the principles of second harmonic restraint and dead angle restraint to distinguish inrush current from fault current are influenced such many factors as the decrease of transformer core magnetic saturation and CT transient saturation. In fact, the inrush current is characterized of its peaky wave and its relatively...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.