Advanced Materials Research Vols. 608-609

Abstract: In recent years, wind power penetration into the grid has increased rapidly with abundant wind resources in Jiuquan, according to the policy of the Chinese government to “establish a ‘Hexi Wind Power Corridor’ and rebuild another Western ‘Terrestrial Three Gorges Dam’”. By the end of 2010, the total installed capacity of wind power in Jiuquan has reached 5160 MW. The wind farms are connected to 110 kV transmission network or above in Jiuquan, the studies of their impacts on the grid, in particular, the grid operation are becoming serious and urgent. Jiuquan is far away from the load center with a weak grid configuration, therefore issues such as transmission line overloading, local grid voltage fluctuation, and transient stability limitation are looming with large scale wind power integration. The power system dispatch and operation are influenced by the intermittent nature of the wind power, which should be regulated by the system reserves. This paper discusses the recent integration of wind power into the grid with a focus on the impact on the Gansu power grid operation. The paper also presents the measures to deal with these issues.

Abstract: With the proportion of wind turbine generation system(WTGS) in power grid is highly increasing, which produces a great effect on the security and stability of the electric power network. Considering the current condition and characteristic of wind form, we built a simulation model in the imitative situation with different wind turbine outputs and different feeder types, obtained the reactive power loss of wind farm and key node voltage, as well as the ability of fixed compensation device. By using the reactive power generated from wind turbine, it can reduce capacity of the reactive compensation device in collection station, which realizes the balance of reactive power, increases the voltage stability.

Abstract: The variable-speed doubly-fed wind turbines (DFIG) were able to participate in frequency regulation by adding an additional frequency control. The influences exerted by the additional frequency control of DFIG units and conventional units governors on system frequency emergency control measures were analyzed. When the power shortage is small, it is recommended to consider the DFIG units to participate in frequency regulation, While a large power shortage it is not recommended.

Abstract: Wind energy is an important strategic energy over the world. Wind power is a useful form of energy conversed from wind energy. The main conversion of wind energy is using wind turbines to make electricity. Generally, studies focus on the specific technology of wind energy. There is, however, little qualitative information on status of wind energy utilization and development. This research tended to focus on systematic analysis of global utilization and development of wind energy, rather than on particular technology. The results shown that from 1997 to 2010, the global cumulative installed wind turbine capacity is exponential growth with years. The top eleven wind energy utilization countries account for 87.7% of total. The global utilization of wind energy increased 24.6% in 2010. The highest increasing country is Romania with an increasing rate of 264.3%. The cumulative installed wind turbine capacity has increased by 73.2% in China, which is the largest cumulative installed wind turbine capacity country. US increased by 14.5% in 2010 as the second cumulative installed wind turbine capacity country.

Abstract: Due to randomness and fluctuation of wind speed, reliability of power system will be affected severely with increasing wind energy injected into power grid. In order to evaluate the effect on reliability of power system with wind farms, the author considers feature of time-sequential and self-correlation of wind speeds and builds an auto-regressive and moving average (ARMA) model to forecast wind speeds. Combining with state models of conventional generating units, transmission lines and transformers, a time-sequential Monte Carlo simulation reliability model is proposed to do reliability assessment of composite generation and transmission system with wind farm. IEEE-RTS test system is introduced to prove the proposed model. Analysis and comparison of results show that reliability can be improved clearly after integration of wind farm.

Abstract: This paper investigates the impact of wind generation consisting of doubly-fed induction generators (DFIG) on the system angle stability. 3 different factors are considered: the penetration level of wind generation, the connection location of wind generation and the reactive power control strategy that the DFIG utilizes. A modified IEEE-3 machine and 10 bus system has been used as the test network and a number of simulations have been conducted. It shows that the higher the penetration level of the DFIG-based wind generation, the better the system angle stability. Compared with unity power factor control strategy, the system stability is better when the DFIG utilizes constant voltage control strategy. Beside, different connection locations of wind generation also have effects on system stability.

Abstract: VSC-HVDC is one of the proven solutions for the transmission problem of offshore wind power. The structure of back-to-back with two-level converters was adopted for wind farm and grid side, in this paper. PI controllers and SVPWM modulation strategy were used for control system. The double closed-loop vector control method was used for converters of two ends, one end controlling DC voltage and the other controlling active power. The reactive power was controlled by both ends independently. The designed system was verified by simulation and experiment based on a small-capacity experimental prototype.

Abstract: Due to highly complex and non-stationary operation condition, a dynamic wind turbine health condition evaluation approach based on multi-source information fusion is recommended. The uncertainty and incompletion of evaluation factors are fully considered, both qualitative and quantitative evidences are integrated. A case study is provided to illustrate the implementation process of the dynamic evaluation approach for wind turbine health condition. It is shown that the proposed approach offers a flexible and effective way of wind turbine health condition evaluation and the result can be used as a support for condition based maintenance decision.

Abstract: The components of wind power cost are analyzed firstly, which provide an intuitive explanation for understanding the composition of wind power generation. And then a two-factor learning curve model is developed for forecasting future price of wind power. We use the model for practical forecasting and simulating wind power cost from 2012 to 2020, the results obtained demonstrate the credibility and validity of the model.

Abstract: Traditional control strategy for wind power converter is dual closed-loop under balanced voltages.With the development of the control theory. The problems of the wind power converter under unbalanced voltages have been considered. This paper analyzes the impact of wind power converter under unbalanced grid fault and propose a new control method.This improved method contains positive and negative sequence current trace under their own synchronous axis.The improved method has good performance under unbalanecd voltages.It shows regulation in DC voltage and sinusoidal in AC current.