A good Black-Start scheme is important and necessary to resume power supply fast and efficiently after black out, and how to choose black-start power is the first thing to consider in the scheme. In this paper, the ad...
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A good Black-Start scheme is important and necessary to resume power supply fast and efficiently after black out, and how to choose black-start power is the first thing to consider in the scheme. In this paper, the advantages of VSC-HVDC as black start power are analyzed. The ability of VSC-HVDC to soft energize major powersystem equipment is proved through simulation by software PSCAD/EMTDC. Simulation waveforms during soft energization are illustrated. These plots have described the good voltage and frequency characteristics of VSC-HVDC. Furthermore, the transition from black start control to normal power flow control is discussed. Simulation results indicate that by using soft energization, VSC-HVDC is an ideal black start power.
In the control of the wind generation, the maximal power point tracking (MPPT) control plays important role in the efficiency. This paper presents the simulation results of the MPPT control with RTDS-based DFIG model....
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In the control of the wind generation, the maximal power point tracking (MPPT) control plays important role in the efficiency. This paper presents the simulation results of the MPPT control with RTDS-based DFIG model. At first, it analyzes the vector-control scheme for the MTTP, which results in independent control of active and reactive power of the generator. And then, it develops the MPPT controller implemented on the rectifier and inverter based on PI control strategic. Furthermore, it builds the DFIG model based on the RTDS with the corresponding technology. And the simulation result with the proposed model verified the control strategy.
Desired islanding detection method not only can detect islanding within acceptable duration, but also require it has less adverse impact on power quality. This paper presents an active islanding detection method for a...
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Desired islanding detection method not only can detect islanding within acceptable duration, but also require it has less adverse impact on power quality. This paper presents an active islanding detection method for a distributed resource (DG) unit which is coupled to a utility grid through grid-connected converter. With the proposed method which is based on adding periodical disturbing current through current controller of the interface voltage-sourced inverter, islanding can be effectively detected. But when the disturbing current remains unchanged, this method still has some shortages, so this article improved it and used a changed time-varying disturbing current ending with faster detecting time and less disturbing. The studies reported in this paper are based on time-domain simulations in the PSCAD/EMTDC environment. And the results show that the proposed islanding detection method always meets the two-second UL detection requirement.
In this paper probabilistic estimation of PCC loss is approached in distribution systems. For the difficulty of directly solving the impedances of the star-connected equivalent model, a port-based model is adopted for...
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ISBN:
(纸本)9781424449347
In this paper probabilistic estimation of PCC loss is approached in distribution systems. For the difficulty of directly solving the impedances of the star-connected equivalent model, a port-based model is adopted for voltage magnitude calculation under four fault types (TPF, SLGF, LLF and DLGF). The specific energy (SE) function is used to evaluate voltage sags involving the voltage magnitude and sag duration simultaneously, and PCC loss is directly computed from the trip probability density, which derives from the normal probability distribution function of SE. The distribution characteristic of balanced and unbalanced faults is also considered. The estimation method for PCC loss is proved fast and effective by IEEE RBTS system.
Along with consuming of fossil energy step by step, crisis of energy has been appeared. The solar energy, which is endless, is a kind of renewable energy. Radiation of sun coming to earth in a day is equal to the ener...
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Along with consuming of fossil energy step by step, crisis of energy has been appeared. The solar energy, which is endless, is a kind of renewable energy. Radiation of sun coming to earth in a day is equal to the energy, which is released by trillion buckets of oil. The research of solar energy generation has stepped into a very activity period. This paper analyses the physics characteristic of photovoltaic array firstly, then researches the mathematical model applying in engineering, and designs the total simulation model based on power electronic circuit in the end. In order to validate the correctness and validity, this paper makes a simulation as an example. The scheme can express the V-I characteristic of photovoltaic array very well.
Fast and accurate tracking of voltage flicker envelope is significant to the performance of flicker meter, flicker source location and the mitigation of voltage flicker. Using the energy of a signal and its shifted si...
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Fast and accurate tracking of voltage flicker envelope is significant to the performance of flicker meter, flicker source location and the mitigation of voltage flicker. Using the energy of a signal and its shifted signals to track the envelope of voltage flicker is presented in this paper. It is assumed that the signal is shifted, once by a lead angle equal to beta, and at another time by a lag angle equal to beta, which generates two new signals u + (t) and u - (t). According to the energy differences, the relationship between the flicker amplitude and u(t), u + (t), u - (t) can be obtained, so the voltage flicker envelope is successfully tracked. How to obtain the shifted signals u + (t), u - (t) is analyzed in the paper. The frequency error e f (%), amplitude error e m (%) and waveform standard deviation sigma(%) are used as the weighing index of the accuracy of tracking flicker envelope. The theoretical analyzing and RTDS simulation test verify that the suggested method is accurate, fast and anti-noise.
The electrical capacitance tomography (ECT) system was used to the visualization of the two-phase flow as well as the measurement of the film thickness in a pulsating heat pipe (PHP). The new-developed micro-sensor wa...
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The electrical capacitance tomography (ECT) system was used to the visualization of the two-phase flow as well as the measurement of the film thickness in a pulsating heat pipe (PHP). The new-developed micro-sensor was also applied as a part of the flow channel, with the characteristics of heat transfer and hydrodynamics similar to the measured tube. The measurement accuracy and the image resolving power were improved as compared with the conventional sensors. So the applied area of the ECT technology was widened. The experimental results indicate that there might exist three flow patterns, i.e. bubble-liquid slug flow, semi-annular flow and annular flow, corresponding to different operating conditions. The measurement results of the film thickness compare well with the actual conditions, and the trend of the film thickness can realize the identification of the flow patterns.
In this paper, based on Centralized Distributed model, a study method of reliability of WAMS is presented. The whole WAMS system is divided into two sub-systems: Monitor Center system and Data Acquisition system. The ...
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In this paper, based on Centralized Distributed model, a study method of reliability of WAMS is presented. The whole WAMS system is divided into two sub-systems: Monitor Center system and Data Acquisition system. The Communication system is also modeled as an auxiliary evaluation system. According to the Markov condition, the Monitor Center system establishes the Kolomogorov equation, sets the invalidation function based on the GO software model, and obtains the evaluation methods of its availability. The analysis of data acquisition system takes the phasor measurement unit and Phasor Data Concentrator (PDC), which installed in various protection areas, as the study objects, and gets the reliability evaluation of data acquisition system by the series system model, the parallel system model and k/n judgment system model of those facility units. The study method is used in the reliability evaluation of a real WAMS system of IEEE 14 Node. As the result shows that this reliability evolution method has a guiding significance in the practical application of WAMS system.
Solar energy is considered as one of the most effective, less expensive, harmless and less environment pollution effect of renewable energy sources. The problem of using solar power including varying weather condition...
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ISBN:
(纸本)9781424449347
Solar energy is considered as one of the most effective, less expensive, harmless and less environment pollution effect of renewable energy sources. The problem of using solar power including varying weather condition brings different output power of the photovoltaic (PV) array, which may cause a serious waste of solar power. For solving this problem, a Maximum power point tracking (MPPT) strategy is always required to make PV array keep giving maximum powerunder different environment condition. In this paper, a variable step MPPT based on gradient descent method is proposed for faster and more precise tracking process. A model based on matlab/simulink was established to analysis the performance of the proposed MPPT strategy. Simulation proves that this MPPT method is practical with a better performance than the traditional strategies.
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