Search

Although the doubly-fed generator group has a flexible ability of reactive power regulation, when a fault occurs in the power system, the ability will be closed to saturation and we need to adopt measures to support network voltage. In this paper, the model of doubly-fed wind turbine、SVC and STATCOM will be given. And the paper will provide a control system of the two dynamic reactive power compensation devices respectively. By power system simulation software Matlab and combining a regional power grid of Mengdon, both SVC and STATCOM are applied to the wind farm and the paper will analyze the characteristics of network voltage. The simulative results show that both the SVC and STATCOM can help wind farm voltage rapidly reconstructed after the fault. In addition, the STATCOM can better improve the transient stability of the wind farm and the compensation effect of STATCOM is better than SVC.

As distribute power generation and micro-grid technology develops, more and more researchers attach importance to the problems of power quality in micro-grid, especially the problem of harmonic. This paper describes the impact and harm harmonic has on the power quality of the power grid. It introduces a revised method of managing micro-grid harmonics which uses an active power filter (APF), and the control method of APF is different from the traditional one. It also establishes the simulation model of micro-grid, analyze the simulation results and experiment in actual micro-grid to verify the effectiveness of the proposed method.

This paper presents a new unit commitment model to solve the uncertainty of wind and load. The chance constrained programming is introduced in this paper. The uncertainty of wind and load is expressed as their prediction error. Considering their different characteristic, wind prediction error is indicated as a fuzzy variable, while load prediction error is represented as random variable. Different confidences reflect the different satisfaction of the constraints. Finally, example analysis shows that the proposed model is feasible and effectiveness.

In view of the disadvantage existing in stochastic programming and fuzzy programming that in the process of modeling of wind power both of them need a huge amount of historical data information to establish precise model, and the advantage of interval planning that it only need to know the upper and lower bounds of the variable in the uncertainty modeling and interval variables contains more information than real variables, this paper puts forward the interval model of the wind power, and use the interval possible degree to deal with the interval constraint conditions. At the same time, this paper adopted the chaotic particle swarm optimization algorithm based on logic from the map to solve the model. Finally, the paper proved the accuracy and effectiveness of the model and algorithm by an example.

This paper presents a multi-objective optimization model to solve the volatility and anti load characteristic of wind power. The pumped storage power station is introduced in this paper. Though pumping and watering, the pumped storage power station can cut peak down to smooth the wind power. Given to the economical efficiency of wind farm, operation efficiency of the wind storage joint system is investigated. In order to improve the wind rate, minimize abandon wind is employed in objective function. To demonstrate the effectiveness of the proposed model, a practical example is tested. The result shows that this model is feasible and effective.

To solve the voltage stability issue caused by wind speed random and fluctuations and dynamic reactive power regulation of DFIG, a new coordinated control strategy is proposed. The scheme of switching of capacitor bank is pre-performed based on the predicted wind power, then based on the variety relation analysis between active power and reactive power of DFIG, by regulating the reactive power of wind farm in real time and determining reactive power output, it implement the reactive power and voltage control. Therefore, this improvement can enhance voltage quality and reduce capacitor responding times. The simulation of a practical example shows that the control strategy is effective and feasible.

Aimed at energy-saving, an intelligent teaching building lighting control system based on PLC is designed. Keeping PLC as the core, the system consists of an illumination measurement module (for measuring the light intensity in classrooms), a statistic module (for counting students in classrooms), a human body existence detecting module (for identifying distribution zones of human bodies in classrooms), and an A/D conversion module. The hardware and main program of the system have been introduced respectively. By using the system, the lights can be turned on or off automatically according to the brightness, the students number and students location in classrooms. The system can also be changed into manually control mode for emergency of PLC fault or other special need.

In view of faults which the traditional genetic algorithm (GA) have such as slow convergence speed and easy to fall into the local optimum. This paper put forward a genetic algorithm which is based on the multi-island group strategy, and applied it to the distribution network planning. The paper has established a planning model which takes the yearly comprehensive cost as objective function and discusses the repair methods of islands, solitary chain and closed-loop to meet with the requirements of grid radial. Finally, the proposed method is planning on a 54-node grid to prove the effectiveness of the algorithm and model.

From the angle of voltage distribution, the influence of DG on power network was studied, various access position and access capacity of DG were analyzed, and conclusion can be drew that DG can help optimize the voltage distribution in the power network. Besides, the output of photovoltaic and wind power was characterized by varying with time, and based on that, the voltage distribution was simulated when they were both connected in the same distribution network. According to the simulation result, some valuable principles and necessary procedures have been proposed.

For the reserve capacity optimization problem of regional power system with wind farms, a joint optimization model was establishes which can effectively reduce the reserve capacity requirements of the regional power system with wind farms. This model was based on chance constrained programming method ,and quantified the processes that subsystems without wind farms providing reserve capacity support to subsystem with wind farms, each subsystem was conditioned by the level of security and stability, and the security constraints of regional system were also comprehensively considered. Monte-Carlo stochastic simulation model of genetic algorithm was used to solve the model. The model was tested by an example, and the results achieved the expected, which shows the model has a high reference value for the reserve capacity optimization of the power system with wind farms.

The doubly-fed wind power generation system containing crowbar protection circuit will change from reactive power source to reactive power load during the low voltage ride-through, which is likely to aggravate burdens to the fault system. Aiming at solving this problem, the paper will introduce the STATCOM compensation device, and put forward a comprehensive control strategy. Under the coordinated control strategy, the STATCOM will cooperate with the compensation capacity of the doubly-fed generator to support the reactive power. The voltage at point of common coupling will be raised and the ability of low voltage ride-through of the wind turbines will be improved. A simulative model of doubly-fed induction generator is established in MATLAB and the strategys rationality and effectiveness will be verified by the simulative results.

This paper took the intensive receiving-end power grid as the research object and analysed the problems of three-phase short-circuit current over-limited of 500kV intensive power grid in the early stage of UHV construction. Firstly, this paper analysed the influence factors of the short-circuit current based on self-impedance analysis model of two-port network theory and the equivalent model of UHV power grid. Then, the applicable current-limiting measures were put forward. Finally, this paper proposed one scheme to solve the problems of three-phase short-circuit current over-limited of 500kV buses in one practical receiving-end power grid and verified the feasibility of this scheme from three different aspects. Aiming at the over-limited influential factors, the applicable current-limiting measures can be taken as follows: separating the 500kV bus at UHV substation, lapping the lines outside the substation and decentralizing the power supplies. The proposed measures can effectively solve the problems of short-circuit current over-limited in the early stage of UHV construction and provide reference for other power grid.

This paper presents an improved particle swarm optimization algorithm (IPSO) to optimal reactive power dispatch and voltage control of power system. The improved particle swarm optimization algorithm introduces the adaptive inertia factor into the classical swarm algorithm to improve the global search capability and accelerate the searching speed. Study the DPSO algorithm to construct the collection of discrete solution values and the collection of discrete velocity values, then the transformer taps and the reactive power source accurately described as discrete value during the whole optimization process. By this way, making the variable expression accurately reflects the actual situation, optimized results are more realistic. The IPSO applied for reactive power optimization is evaluated on an IEEE 30-bus power system. Simulation results compared with the others same type algorithms, proved its effectiveness and superiority.

This paper is discussed the steady-state model of Double Fed Induction Generator (DFIG) and Fix Speed Induction Generator (FSIG). The Wind Turbine Generating Systems (WTGS) buses can be treated as only PQ buses (with P and Q varying across iterations in contrast to a conventional PQ bus where they remain constant)when connected to distribution network. A genetic algorithm considered WTGS is proposed and applied to solve the reactive power optimization problem. The proposed method is carried out in a modified IEEE 33-bus system. The study cases show that the proposed method is feasible and provides a reference value for the operation of wind generation system.

As the connection between transmission network and consumers facilities, distribution network has been paid more and more attentions about its planning.A scientific and efficient optimization project for distribution network structure can save investment,reduce power-cutting and the line losses, as well as improve the quality of electric power,which is currently one of the important task of the departments of power system.This paper introduces chaos into the distribution network planning,and a new planning method is based on the particle swarm optimization. A restoration scheme is given aiming at the problem of production of the lots of infeasible solutions due to the application of the genetic algorithm in distribution network planning.And the improved forward-backward sweep method of distribution network is given based on analytic network process.The restlts from calculation example shows that the proposed method is effective.

In this paper, using this sensitivity algorithm to analysis of the problem of weak voltage area. After that, using the improvement of the traditional swarm algorithm to recover the weak volatage area. In this article, the inertial factor, the convergent factor and are introduced into the swarm algorithm. The model of the weak voltage recovery which is object to the minimization of the sensitive analysis result and the power loss, and the constraint conditions are introduced. Then the improved swarm algorithm is used as the tool to solve this model and find an ideal solution.