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During transients, the instability of the power system can attribute to the angle instability as well as the voltage instability. The angle and voltage stability are entangled with each other during transients. This paper proposed a direct approach to determine the types of instability of power systems during transients. Based on differential algebraic equations of the systems, the equilibriums and...
Accurate prediction of wind speed is of great significance to the operation and maintenance of wind farms, the optimal scheduling of turbines and the safe and stable operation of power grids. This paper puts forward a new method for short-term wind speed forecasting based on the wavelet packet decomposition(WPD) theory and an improved Elman neural network(ENN), and the concrete application steps of...
The integration of a large amount of wind generators to the power system may pose new issues to its control and operation. One of important issues is that low frequency oscillation may be induced by the variation of the wind power, which is also referred as forced low frequency oscillation. To analyze the mechanism of the forced low frequency oscillation of the wind-integrated power system, a 7-order-model...
With a large number of wind farms integrated into power systems, the load characteristics of the power systems will vary, resulting in the inapplicability of the traditional load model. Thus, it is of great importance to describe the load characteristics of power systems by taking the impact of the integration of the wind power into consideration. This paper first discusses the influence of wind power...
Due to the presence of significant non-linearity in the power system, linear time-delay models which are often used in many existing literature are unable to characterize their dynamics. This paper introduces a novel modeling method, based on which we design a nonlinear controller for the time-delayed power system, including an excitation controller and a turbine valve controller for the steam turbine...
The charging load of plug-in electric vehicle (PEV) is usually modeled with statistic methods such that the internal physical relationship among the charging factors is ignored. In this paper, a diffusion model for charging power of PEVs is proposed. The proposed model considers the interactions among the charging factors in a mathematical way using the physically-based modeling method. The area control...
As the application of electric vehicles expands, their charging power demand will influence the operation of the power grid. This paper firstly considers the relevant factors which influence the charging power demand; by using the Monte Carlo method to calculate the large-scale electric vehicle charging power demand. Based on the problem that the large-scale electric vehicle's disordered charging...
The desirable scheme of capacitor placement in distribution systems aims at achieving voltage regulation and power loss reduction, while preventing harmonic resonance or magnification. The author proposes the reactive power optimal model for distribution network under the harmonic distortion, configuring the selected node for capacitor by the sensitive method under the harmonic distortion, and solves...
The unified power quality conditioner (UPQC) has the function of voltage-current compensation devices. To enhance its comprehensive compensation effect, this paper combines the traditional PID regulator and fuzzy control theory and designs a fuzzy-PID controller to apply in UPQC DC-link capacitor voltage control links and tracking control link of the compensation. The method synthetizes the strong...
The traditional control strategy of active power filter (APF) has low accuracy and bad robustness. Firstly, a state-space model of shunt APF is established. Taking errors as unknown disturbance to the system, a robustness controller is designed based on the Hinfin control theory. Secondly, the fuzzy PI control with self-adjustable factor is applied in the DC-link voltage control of APF. The self-adjustable...
Because of the H2/Hinfin control has good robustness and performance, the H2/Hinfin control strategy of SVC is designed for improving the voltage characteristics, damping system oscillation. In the three-phrase short simulation, the transient responses of the main parameters of the H2/Hinfin controller and the conventional controller are compared and analyzed. The result demonstrates that the H2/H...
Harmonic suppression is one of the focal facets of power quality problems. An important trend of harmonic suppression is to apply the active power filter (APF) in power systems. The strategy of APF control is a researchful hotspot. Hinfin control theory, which can make optimum design to control systems, has high control accuracy and satisfactory robustness. It also has clear physical meaning and strict...
The entropy is a measure of uncertainty and has been widely applied to almost all disciplines. The purpose of this paper is to give an overview of the applications of entropy principles in power systems to attract more researchers to carry out further research in this field. Firstly, fundaments of entropy principles are introduced. Secondly, the current applications of entropy principles in power...
Based on the mathematic model of UPFC, the capability of voltage regulation and power flow control of UPFC is discussed in this paper. A major fuzzy controller with self-adjustable factor of UPFC is put forward. The controller realizes decoupling control of shunt side and series side of UPFC by unique disposal. Furthermore, a supplementary fuzzy controller with use of the power flow as controlling...
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