Advanced Materials Research Vols. 724-725

Abstract: The paper mainly studies the available transfer capability of wind farm incorporated power system, and proposes an on-line calculating method considering many uncertain factors. First based on continuation power flow, an improved algorithm of the key constraint by linear prediction is proposed so as to obtain deterministic ATC with the expansion power flow equation. Then Monte Carlo simulation is used which takes many uncertain factors into considerations, such as wind speed, the random fault of generators and lines, the fluctuation of generators and load, etc. With hierarchical clustering algorithm, the samples with the same key constraint can be divided into one category without repeatedly predicting key constraint, so the probabilistic ATC in all kinds of conditions can be got rapidly and precisely. Finally a case study demonstrates the validity and superiority of method proposed in this paper. The research could be a valuable reference to power market operations and wind farm planning.

Abstract: According to the weibull distribution of the wind speed, this research establishes the probability outrage model of the wind generator. Besides, this paper establishes a three-state Markov reliability model of the wind generator taking the drop running state into account. And the load model is built considering the randomness of the prediction error. This paper takes the improved IEEE RTS79 system for example, the reliability index of loss of load probability and loss of load expectation are calculated. Because the wind turbine derating state and load error are taken consideration, the proposed model is more accurate and the assessment results have high practical significance.

Abstract: Aiming at the fault characteristics of high-speed gearbox fault diagnosis of wind turbine, a fault diagnosis method of combining wavelet analysis with least square-support vector machine (LS-SVM) is proposed. According to the method, the energy of frequency bands generated by wavelet decomposition and reconstruction of the high-speed gearbox's vibration signals in different fault states is normalized as eigenvectors, forming training and testing samples of LS-SVM fault classifier. Train the LS-SVM fault diagnosis model with the training samples and test the accuracy with the testing samples. The result of research shows that the fault diagnosis method based on the wavelet analysis and LS-SVM has good diagnostics effect.

Abstract: The improved maximum power point tracking (MPPT) control based on the reduction of tracking range could reduce the tracking distance of wind turbine effectively, and improve the tracking efficiency. In this study, the relationship between the compensation coefficient of the improved MPPT control and several factors was investigated. Based on simulations of the simplified wind turbine model, wind conditions, air density and wind turbine parameters were used in the studies to investigate the relationship between the optimum compensation coefficients and these corresponding conditions. It can be indicated that in the fact, compensation coefficient is majorly determined by the tracking targets of MPPT and the dynamic performance of wind turbines that determined by the conditions mentioned above. The results also provide guidance for further studies in this area.

Abstract: Renewable energy is the development tendency in the future. Its not only save energy but also protect the environment. And the wind power generation has more competitive potential compared with other renewable energy, so it develops so quickly. According to the bad environment of the wind farms, wind turbines control system requires multipoint, high speed and real-time communication. This paper puts forward a kind of wind turbines control system based on the CAN bus architecture and realizes the real-time communication and decentralized control between the master control system and submodule. This paper analyses the system structure, the hardware composition of control module, the expansion of CAN bus, the communication mechanism in master-slave module.

Abstract: Actual survey the vibration data of domestically produced megawatt level wind-driven generator gearbox at different rotational speeds, Extract the parameters of time-domain characteristic, analyze the three dimensional frequency spectrum through the MATLAB software, contrast two same model, same specification wind-driven generator's vibration situation, identify the resonance area of wind-driven generator, and determine the existence of one of the generators shaft misalignment fault. Provide a reliable basis for the safe operation of wind-driven generator.

Abstract: The 3D model of bolt connection between flange and yaw gear was established in Pro/E and pre-processed in Hypermesh. Then build the contact model of bolts in ABAQUS and analyzed the statics performance by taking different preload in two kinds of working condition, which stimulated the preload and limit load condition. The results show that, through comparing the stress strength under different preload condition, the author puts forward a value range of preload for reference: F_v = (0.6~0.8) A_S · σ_p0.2. The research provides a reference for strength check, fatigue analysis etc. of the bolt connection on yaw gear of the MW wind turbine generator system and other bolt connection systems, to facilitate further optimal design.

Abstract: The main purpose of this paper is to study the enhancement of the Low-Voltage-Ride-Through (LVRT) capability of the wind farm with the installment of the Static Synchronous Compensator (STATCOM) and the Static Var Compensator (SVC). With more penetration of wind energy from on-shore and off-shore wind farms, utilities have been starting to set up the regulation requiring the wind turbine generators to remain connected to the grid when a fault takes place in the system which is referred to as Low-Voltage-Ride-Through (LVRT). A wind farm composed with doubly fed induction generators is used as the study system. Both the STATCOM and the SVC are utilized as the devices for enhancing the LVRT capability of the wind farm. The results are demonstrated for comparing the performance of the two devices in the improvement of voltage dynamic characteristics of the study system.

Abstract: Accurate wind speed forecasting of wind farm is of great significance in economic security and stability of the grid. In order to improve the prediction accuracy, the paper first proposed a spatio-temporal correlation predictor method. Based on physical characteristics of wind speed evolution, the method looked for the wind speed and direction information at sites close to the target prediction site, and established STCP model to forecast. And then we established the BP neural network to finish multi-step forecast with wind speed time series of target forecast site .Last, two methods were combined to form STCP-BP method. Simulation tests are conducted with operation data from certain wind farm group in China and results show that STCP-BP method can effectively improve the prediction accuracy compared with BP model.

Abstract: Briefly introduces the development trend of wind power and the various energy storage technologies in wind power system, include their principles, advantages, disadvantages and development prospects. Challenges for large-scale wind power integration are summarized. With regard to the problems in power quality, stability, economic, low voltage ride-through (LVRT) ability induced by the grid integration of wind power, the recent progress of solutions based on the energy storage technology is discussed, and the advantages and disadvantages of various schemes are analyzed. Based on the existing research achievements and the characteristics of the energy storage technology, some suggestions have been put forward on assure the stability of the electric power grid and power supply quality.