Research On The Key Technology Of Wind Power Generation System

With the development of the economy, people need to find new energy sources. Wind power generation with its rich resources and technical advantages, becomes the current research and development focus at home and abroad. Researches on wind power technology in China started lately, Especially basic research, experimental research and application of new technologies of control system have a great gap compared with foreign countries. Therefore, it has important meaning to research the key technologies and related theories of wind power reneration technologies.In this paper, with the research object of control system of wind power generator, studies some key questions on wind power control system. The main contents of the full text are list as follows:1. Wind power prediction is studied. By analyzing the high nonlinear process, non-stationary process and chaotic characteristic of wind speed model, a wavelet neural network prediction model of wind speed based on phase space rconstruction is established.(1)The high nonlinear process of wind speed is analyzed. The non-stationary process of wind speed is determined through using the autocorrelation function method. Chaos characteristic of wind speed is determined through using the power spectrum method. A prediction model of wind speed is established.(2)Aiming at the chaotic characteristic of wind speed, using G-P(Grassberger-Procaccia) method to calculate the correlation dimension, and using Takens embedding theorem to obtain embedding dimension, input dimension of model is set by embedding dimension of phase space reconstruction, avoiding arbitrary input node number selection so that the resulting expression is not necessarily the expression of the solution space.(3)Using wavelet transform to decompose non-stationary, the number of hidden layer of wavelet neural network is determined, which can effectively solve the problem of nonlinear and non-stationary wind speed sequence. The model structure and learning algorithm is given.(4)By a half hours wind speed data of30days of China’s zhejiang hangzhou bay estuary(north latitude30, east longitude120), the prediction model of wind speed is verified by experiments. The result shows that, this model is obviously superior to the traditional method.2. The power control problem of the variable speed constant frequency doubly-fed wind turbine is studied. Based on the characteristics of doubly-fed wind power generation system, a new integral variable structure controller based on exponential reaching law is proposed to achieve the doubly-fed motor active power and reactive power decoupling control.(1)Based on maximum power feedback control strategy, the maximum power tracking of doubly-fed wind power generation system is implemented; Based on the stator voltage oriented vector control strategy, the doubly-fed motor active power and reactive power decoupling control is implemented.(2)Aiming to complex structure and not-strong robustness of conventional vector control strategy of doubly-fed wind turbine, a integral variable structure controller is proposed, realizing floating control of rotor current in the rotor static abc coordinate system, avoiding the coordinate transformation of rotor current and simplifying control structure. Sliding mode variable structure control for the parameter variations and external disturbance has good robustness, that can effectively inhibit motor parameter variations and external disturbance effects on doubly-fed wind power generation system.(3)Integral is introduced in the variable structure control with sliding surface, which can eliminate steady state error caused by the variation of motor parameters and external disturbance, but also by adjusting the parameters of the integral part, improve the dynamic quality of the sliding movement. Switch discontinuities essentially of variable structure control cause system chattering, by using the exponential reaching law, the dynamic quality of sliding mode arrival process is guaranteed and the chattering of the system is weaked.(4)Theoretical derivation and simulation result verity the correctness and feasibility of the control strategy.3. Yaw control problem of wind turbine is studied. A sliding mode speed controller for yaw control system is proposed, that implement the yaw induction motor rotor flux oriented vector control.(1)When wind direction has a small change, the wind yaw angle is difficult to accurate control for control strategy based on the wind sensor. When the wind direction change is small, the maximum tracking algorithm based on power detection is used, in order to solve within a small range of wind direction sensor is difficult to determine the wind direction angle problem, improve the accuracy of yaw control.(2)Because the wind speed detection and yaw control has a lag, by using wavelet neural network prediction model based on phase space reconstruction for wind speed short-term prediction, the yaw control in advance of wind turbine according to prediction wind spee is carried out, that can achieve the best generation of wind turbine, reduce the impace of wind turbine, protect and extend the life of wind turbine.(3)Because the yaw system is larger external disturbance, based on the rotor field oriented of the yaw induction motor, a sliding mode speed controller is proposed and the design method is presented. Sliding mode variable structure control in the motor parameter variations and external disturbance has completely robustness and can effectively improve the stablity and robustness of yaw system, improve the accuracy of the yaw wind.(4)Theoretical derivation and simulation result verity the correctness and feasibility of the control strategy.4. A set of small and medium sized wind turbine controller is designed. The actual operating results show that the control methods and strategies of the paper is feasible and effective.(1)It achieve signal acquisition and processing of wind power system、yaw control、automatic untwisting、grid control、parking brake control、safety protection system、in situ monitoring and remote monitoring.(2)Hardware and software of the yaw control and power control is mainly introduced.(3)Through the experiment testing, analysis of the results verify the effectiveness of the control device and related algorithm.