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This paper analyzes the structure, the operating characteristics and the control strategy of microgrid. Based on the requirements of power quality and research achievements of the traditional power system, it is considered to introduce the Dynamic Voltage Restorer (DVR) in power distribution system with microgrid to improve the power quality. A method to detect voltage sags is presented, which incorporates...
In the beginning, a brief introduction of Yimin-fengtun TCSC equivalent system in 2010 is given and the problem required to be solved is put out consequently. In the second section, after a statement of the close-loop impedance controller, various performances of TCSC involving steady-state and transient-state are investigated and the results of relevant simulation on RTDS are presented. In the last...
With characteristics such as impact, asymmetric and nonlinear, the electromotive in electrified railway is a typical kind of single-phase load. Electrified railway connected to power grid will bring a lot of power quality problems. To solve harmonic problems and three-phase voltage unbalance caused by the negative sequence, this paper proposes an integrated management of power quality problems based...
A practical single-phase hybrid active power filter for electric traction system is proposed. This system consists of an active filter, a passive filter, fundamental series resonance circuit (FSRC) and a coupling transformer. With FSRC in parallel and a capacitor of 3th-order filtering branch in series, the active power filter is immune to the effects of high fundamental voltage and current. Thus,...
This paper firstly introduces the principle and structure of voltage source typed power conditioning system (PCS). And then it studies the direct power control method of PWM voltage source converter which is applied in the voltage typed superconducting magnetic energy storage (SMES) system. A proper switching vector table is used in the proposed control method, and a direct power control method for...
Doubly fed induction generator (DFIG) wind turbines are widely utilized as a promising form of electricity generation. Now the great attention is paid to the dispatch, protection and control of power systems integrated with large capacity wind power. In this paper, the mathematical model of DFIG wind turbines is built in PSCAD software. Simulation and analysis of three type of asymmetry fault are...
This paper proposes a wavelet transform approach for the evaluation of harmonic contents of power system waveforms. In this approach, the discrete wavelet packet transform is presented to decompose the waveform, and then based on the decomposed coefficient the harmonic contents include frequencies, amplitudes and phases are calculated by continuous wavelet transform. The wavelet transform is introduced...
The paper presents an iterative process to calculate the voltage magnitudes and phase angles at each bus in a power network for each harmonic frequency (include fundamental frequency). The method indicated in the paper is based on Newton-Raphson method. A six-pulse line commutated converter and a twelve-pulse phase control delta-star connected converter are studied. They are regarded as harmonic sources...
With the development of modern electricity equipment, voltage dips may bring more and more economic losses, which need a proper method of evaluation. In this paper, a time varying quality loss function, utilizing the Tobit model, is used to predict economic losses due to voltage dips. This quality loss function is more flexible and closer to practical situation.
This paper applies the forced power oscillation theory to explain the phenomenon of two power oscillation events recorded by grid wide area measurement system (WAMS). By analyzing the characteristics of the recorded data, we have described the difference between the two events and the negative-damping oscillation events. Calculation and simulation have been performed based on the single-machine infinite...
The mathematical models and power balance relation of VSC-HVDC under AC voltage unbalance were studied in this paper. Based on the mathematical model and the power relations, a kind of negative sequence voltage compensating control strategy was proposed to suppress the negative sequence current. To provide accurate and quick tracking of the generated active and reactive current trajectories, deadbeat...
As the probabilistic load flow (PLF) approach is often applied in the assessment the voltage in the distribution system with the distributed generation, the intermittent power output of the distributed generators (DGs) should be more considered. The power variation characteristics of load and distributed generators should be treated separately. In this paper, taking the PV arrays for the typical example,...
As the wind power generation technique is improved greatly, permanent magnet synchronous generator (PMSG) is paid more and more attention because of its multiple advantages. Nevertheless, conventional directly-drive PMSG wind generation system is connected to the grid by AC transmission. This paper introduces the DC connection structure of wind farm based on PMSG. According to VSC-HVDC (Voltage Source...
In deregulated market, available transfer capability (ATC) is a market signal refers to the capability of a system to transport above already subscribed transmission uses. It can provide significant information for power market participants. This paper deals with the evaluation of ATC for the integration of HVDC link with an AC power system. The computational model of ATC for AC-DC transmission system...
In this paper, firstly the defects of current algorithms for optimal power filter planning are analyzed, and then a new model, taking both filter costs and network loss as objective functions is proposed. In this model, reactive power compensation is also taken into account. Fast nondominated sorting genetic algorithm (NSGA-II), a new multi-objective genetic algorithm, is used to solve the model....
In this paper, present situation and the features of wind power generation in China is introduced briefly, and the significance of determining wind power penetration percentage of wind farm is pointed out. According to the previous research, wind power penetration limit and short circuit capacity ratio are considered as the two main aspects, when wind power capacity limit is focused. The advantages...
With global environment problems increasing, wind power as a renewable energy is concerned worldwide, many wind farms are designed recently, however, the power output of wind farms is fluctuant which is determined by the intermittent and random of wind speed. With the increase of wind farm capacity and the percentage of wind power in the whole power system, the influence of the power output fluctuation...
Doubly-fed Induction Generator (DFIG) is a kind of variable-speed constant-frequency (VSCF) wind generator (WG) which can output reactive power when not working in the constant power factor mode and be used as a reactive power supply for wind farm. In this paper, an optimal control strategy for reactive power in wind farms consisting of DFIG is proposed by combining the reactive power compensation...
Based on actual characteristic of Chinese power system, starting from the practice, this paper puts forward auxiliary service compensation mechanism designing principles in present Chinese power market. Following the spirit and the idea of provisional measures of auxiliary services management of the grid-connected power plant, combining the actual situation of wind power in China, this paper studies...
Distributed generation (DG) that uses renewable energy sources (such as solar and wind) has an unstable output and this can negatively affect existing electric power systems. In order to reduce above impact, we need to control the output through individual DG installed in a micro-grid. This Paper designs a grid-connected Photovoltaic (PV) system based on the multi-type composite energy storage. First,...
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