Abstract
Variable pitch control is an effective way to ensure the constant power operation of the wind turbines over rated wind speed. The pitch actuator acts frequently with larger amplitude and the increasing mechanical fatigue load of parts of wind turbines affects the output quality of generator and damages the service life of wind turbines. The existing switching control methods only switch at a certain threshold, which can result in switch oscillation. In order to deal with these problems, a multi-mode soft switching variable pitch control strategy was put forward based on Takagi-Sugeno (T-S) fuzzy weighted to accomplish soft switch, which combined intelligent control with classical control. The T-S fuzzy inference was carried out according to the error and its change rate, which was used to smooth the modal outputs of fuzzy control, radial basis function neuron network proportion integration differentiation (RBFNN PID) control and proportion integration (PI) control. This method takes the advantages of the three controllers into consideration. A multi-mode soft switch control model for variable pitch of permanent magnet direct drive wind turbines was built in the paper. The simulation results show that this method has the advantages of three control modes, switch oscillation is overcome. The integrated control performance is superior to the others, which can not only stabilize the output power of wind turbines but also reduce the fatigue load.
Highlights
With the decrease of fossil fuels and the increase of human awareness of environmental protection, the attracting attention is giving to renewable resources, especially wind energy [1,2,3]
The response of pitch angle is adjusted more smoothly and quickly with higher precision and smaller fluctuation by using the T-S fuzzy weighted multi-mode control compared to the others as seen in Fig. 16, the rotor speed and power close to RBFNN PID during 0-5 s and to proportion integration (PI) control during 6-10 s described in Fig. 15 and Fig. 17, the higher precision guarantees the output power of the generator stabilize to rated power and smaller fluctuation reduce the mechanical fatigue load of wind turbines
The constant power operation of the wind turbines over rated wind speed caused the pitch actuator act frequently and the increasing fatigue load of parts of wind turbines, which affected the quality of the output power and the service life of wind turbines in the existing variable pitch control schemes
Summary
With the decrease of fossil fuels and the increase of human awareness of environmental protection, the attracting attention is giving to renewable resources, especially wind energy [1,2,3]. Variable pitch control system is one of the important parts for variable-speed constant-frequency wind turbines, which is usually used in medium or large wind power systems [5]. The objective of control scheme is to keep the constant power operation and decrease the fatigue load of parts of wind turbines [6]. MULTI-MODE SOFT SWITCHING CONTROL FOR VARIABLE PITCH OF WIND TURBINES BASED ON T-S FUZZY WEIGHTED. (Ren, et al) proposed a novel pitch control strategy based on bee colony algorithm which shows the good robustness but the bad stability of wind turbines [16], when the wind power system appears random disturbance, the control system is prone to instability. A new variable pitch control scheme based on T-S fuzzy inference is proposed to ensure the constant operation of wind turbines above rated wind, which combined the intelligent control with classical control. According to the error and its change rate, which is the difference generator’s speed and its rated rotor speed, the switch between three controllers makes use of the T-S fuzzy inference and uses the weighted average method to output the coefficients, the synthetic output adopts the weighted sum method
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