Considering the displacement current in the multi-layer soil, the formulas of the ground return impedance and the Fresnel reflection coefficients are derived in frequency domain. These expressions are valid for discre...
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The constituent of Capacitive Voltage Transformer (CVT) are almost capacitances in primary side, and they act essentially as a short circuit to the transient current produced by a switching operation, which will gener...
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Overvoltage in power system restoration must be verified. The basic principle of VSC-HVDC (voltage source converter based high voltage direct current transmission) is briefly introduced. VSC-HVDC has such characterist...
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ISBN:
(纸本)0863412467
Overvoltage in power system restoration must be verified. The basic principle of VSC-HVDC (voltage source converter based high voltage direct current transmission) is briefly introduced. VSC-HVDC has such characteristics as flexible operation and control modes, independent control of active and reactive power, and operation on four quadrants. The overvoltage of the overvoltage between AC transmission line and the line connected with VSC-HVDC are calculated by theory analysis and simulation on PSCAD/EMTDC. The comparison of those overvoltage shows that the overvoltage of long AC transmission line connected with VSC-HVDC is lower than that of pure AC transmission lines. So the application of VSC-HVDC can enhance the speed of power grid restoration.
Offshore wind farms based on doubly fed induction generator (DFIG) are generally connected to the AC system via long submarine cables. Integration of offshore wind farms with HVDC transmission based on voltage source ...
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ISBN:
(纸本)0863412467
Offshore wind farms based on doubly fed induction generator (DFIG) are generally connected to the AC system via long submarine cables. Integration of offshore wind farms with HVDC transmission based on voltage source converter (VSC-HVDC) is an advantage due to its regulating properties. This paper analyzes the need for coordinating the control of DFIG and VSC-HVDC link so that the two topologies can work together. Stator flux oriented vector control technology is used to execute AC excitation for DFIG rotor, then independent control of active and reactive power is realized and electricity generation by capturing maximal wind energy with high efficiency is also obtained. The control objective of VSC-HVDC is delivering the generated power to the AC network instantaneously and to keep AC voltage at wind farm bus constant. Interactions between DFIG and HVDC link are investigated and simulations performed in PSCAD/EMTDC to verify the proposed control strategy.
In this paper, a fuzzy excitation controller based on wide-are measurement system (WAMS) is built, in which the voltage deviation and its rate are introduced as the input of main-controller, while the deviation and co...
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ISBN:
(纸本)0863412467
In this paper, a fuzzy excitation controller based on wide-are measurement system (WAMS) is built, in which the voltage deviation and its rate are introduced as the input of main-controller, while the deviation and corresponding rate of local generator's frequency and center-of-inertia frequency are acted as the input of the second controller to indicate the global information. The multi-machines system model is firstly set up with MATLAB/PST. Then the digital simulation is conducted to compare the influences of PID excitation controller and fuzzy excitation controller based on WAMS on the transient stability. Results show that applying the fuzzy excitation controller proposed in this paper, the ability to endure serious disturbances can be strengthened and transient stability can be improved.
Because the compensation signals of DVR are unpredictable, this paper advanced a deadbeat control algorithm for DVR voltage waveform tracking compensation. On the basis of state equations and state variables informati...
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ISBN:
(纸本)0863412467
Because the compensation signals of DVR are unpredictable, this paper advanced a deadbeat control algorithm for DVR voltage waveform tracking compensation. On the basis of state equations and state variables information of the system, a specific scheme is produced to realize voltage waveform tracking compensation, which includes a state observer a voltage forecast and a current forecast for a random load. The switch control signals of next sampling period are calculated so that the output voltage can track the reference voltage synchronously. The simulation results show that this control algorithm is correct and feasible.
VSC-MTDC has attracted increasing attention because of its excellent characteristics. Its connection type is one of the key points in research works. Three basic connection types including Parallel, Series and Hybrid ...
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ISBN:
(纸本)0863412467
VSC-MTDC has attracted increasing attention because of its excellent characteristics. Its connection type is one of the key points in research works. Three basic connection types including Parallel, Series and Hybrid are analyzed and their characteristics are discussed in this paper. Through the analysis on VSC equations in dqO coordinate system, constant DC voltage PI controller and constant power PI controller are designed. On the basis of establishing MATLAB simulation models, the simulations of three connection types are conducted. Simulation results show that the proposed connection types of VSC-MTDC are feasible and the characteristics of them are verified.
This paper analyzes characteristic harmonic currents of TCR and presents a method to reduce the harmonics by means of phase-shift transformer. It also introduces the constitution and implements methods of compensating...
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Combining electricity market dynamic model proposed by Alvarado, this paper uses differential/algebraic equations and eigenvalue techniques to study the stability of electricity markets. The necessary and sufficient c...
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ISBN:
(纸本)0863412467
Combining electricity market dynamic model proposed by Alvarado, this paper uses differential/algebraic equations and eigenvalue techniques to study the stability of electricity markets. The necessary and sufficient conditions of judging electricity market stability and asymptotical stability are provided. As well as the sufficient conditions of judging electricity market unstable and asymptotical unstability is presented. The obtained conclusions removed the condition of Yang's with the assumption "the matrix is square and nonsingular" and other conditions. Using these stability conditions may directly judge the electricity market model stability by the initial data. In addition, the theoretical results in this paper can be used to reasonably explain the unable phenomena of electricity market proposed by Alvarado.
This paper researches profoundly on the coordinated control of UPQC (Unified Power Quality Conditioner). By analyzing the radical reasons of coupling effect between UPQC series unit and shunt unit, a simple and practi...
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