Applied Mechanics and Materials Vols. 672-674

Abstract: The effects of flexible tower supporting on wind turbines helical gear system was discussed. Using speed-combined method, the random speed model of wind was established and the wind loading was obtained. The helical gear system model of wind turbine was built under flexible supporting of the tower. The vibration displacement responses of each shaft were simulated and compared with response under rigid supporting. The results shows that the amplitude of vibration displacements under flexible supporting are generally higher and closer to the actual working condition, and considering the effects of flexible supporting of tower on system is necessary to the dynamic analysis.

Abstract: Large-scale offshore wind power has been developed in recent years, and two possibilities are considered for the transmission system between the offshore wind farms and the onshore grid: VSC-HVDC and HVAC. The paper aims to compare both systems for 300MW offshore wind farms, 25 km, 50km and 75km from the Point of Common Coupling on an economic basis using a DCF(discounted cash flow) analysis. A linear fit to the net present values has been made, obtaining the break-even distance of 47km. When the transmission distance is shorter than 47km, the HVAC system is more economic, otherwise the VSC-HVDC system is a more cost-efficient option.

Abstract: Low-frequency oscillation characteristics of AC / DC system with DFIG-based wind farms were studied. Detailed mathematical pure AC and AC / DC system model were established by considering the effects of doubly-fed wind turbine model and DC transmission dynamic model to do small signal stability analysis. The computed results of small signal stability of DFIG-based wind farms integrating pure AC CEPRI36 nodes system or with DC transmission that operated in four connection modes including bipolar neutral grounding at both ends mode, monopole ground return mode, monopole metallic return mode , monopole and two parallel conductor mode with earth return were investigated by using modal analysis method. Then, the characteristics of local oscillation modes and inter-area oscillation modes were respectively analyzed under the two operation modes of the wind farm participating active power dispatching and reactive power dispatching and consequently some new conclusions were drawn.

Abstract: Wind/solar hybrid system optimization is a key point for cost control. Here a multi-object optimization model is raised. Then a multi-object optimization method based on GA is used to find the Pareto solutions of wind/solar hybrid system. The test data shows that this method can get a good result.

Abstract: When larger scale of small hydropower and wind power exist in power system, the traditional reserve capacity algorithm is no longer applicable at the same time of reducing the carbon emission. Aiming at the volatility and non-regulatory of small hydropower and wind power, considering the forecast error of small hydropower, wind power and load,the unit outage rate and other factors, combined with the actual operation parameters of one regional power system in Southwest of China, the wind-hydro – thermal power coordinated operation of multiple objective function optimization calculation model of reserve capacity is established. Using the weighted coefficient method of unified objective method, it transforms the multi-objective optimization problem into a single objective optimization one. Applying the exterior penalty function method, the constrained optimization problem is changed into a non-constrained optimization one. The improved particle swarm optimization algorithm is got by introducing the particle concentration cognition into traditional particle swarm optimization algorithm. The simulation results verify the validity of the model. To Compare them under different strategies, this method can get less fuel expenses of thermal power units in the case of lower loss of load probability (L_OLP).With the small hydropower and wind power output size to optimize the spinning reserve capacity. The model and the algorithm are helpful for drawing up optimization strategies of the reserve capacity in those regions in which larger scale small hydropower and wind power exists.

Abstract: With the expanding of the scale of wind farm, wind farm’s impact on power grid becomes more serious, which would cause a lot of problems. This paper mainly focuses on the static stability for the power grid containing wind farms. The static stability margins at different wind farm outputs are obtained using continuous power flow method. Their probability distribution is also obtained with wind speed’s Weibull distribution and the relation between wind speed and wind turbine output. Taking IEEE14 model with wind turbines connected as an example to analyze, the results have stated that wind farm output fluctuation has certain impact on the static stability of grid.

Abstract: With large-scale wind power integrates into power system, the risk brought by the uncertainty of wind power output can no longer be neglected. Under this circumstance, the operation risk due to the uncertainty of wind generation and the contribution of wind power to energy conservation and emission reduction are quantified, and the corresponding quantified operational cost, environmental cost and operation risk are being integrated into the economic dispatching model to establish a multi-objective optimization dispatch model. Non-dual interior point method is used to solve the optimization problem. The method is applied to Hebei Southern power grid, simulated with actual wind power output data of one typical day. Simulation results show the rationality and effectiveness of the proposed method.

Abstract: According to the characteristics of the wind farm measuration and the impact of bad data on the state estimation, this paper introduces the reference value of measurement type and the bad data reference factor into the weight function, and then presents the calculation method of state estimation method for solving residual contamination problem caused by large-scale wind power integration. In order to improve the software computing speed and the data section real-time performance of robust state estimation, using parallel algorithms to do Givens transformation. Finally, the simulation tests of a regional power grid to prove that the proposed method can effectively identify telemetry bad data of wind farms eliminate residual pollution caused by it, which improve the speed and accuracy of the State Estimation.

Abstract: An important factor affecting the integration of large-scale wind power is whether there is sufficient peaking capacity. If the peaking capacity is insufficient, we cannot make full use of wind power. Therefore it’s of great significance to study the peaking gap of the power system. This paper defined the peak-load regulating demand continuous curve and proposed the calculation method of the peaking gap based on non-sequential Monte Carlo simulation method. Taking wind power’s random fluctuation and the unit forced outage rate into consideration, the calculation method effectively reflect the peaking capacity needs of the system, which is helpful for determining the appropriate wind power integration.

Abstract: The distribution of neutron flux is simulated by MCNP code from reactor start-up to criticality when the control rods are drawn different length from reactor core on ex-core detector area of the WWER reactor of TianWan. Because physical model built is very large, in order to save calculation time, the moving process of control rod is simplified. The results of calculation show that The neutron mainly distributed in the range of 0-400cm outside the pressure vessel. The value of the relative neutron flux ex-core is maximum in the range of 110cm to 180cm, so detection effect is better when the detector is set in this region.