EMC Study Of Pitch System On MW Wind Turbine

Variable-pitch wind turbine has been became one of the most mainstream forms on MW wind turbine, it can be achieved in a wide range of wind speed. Variable-pitch system can adjust the angles of blade, and optimize the efforts of wind round to improve the output of wind-power characteristics, and eliminate the changes in air density and surface roughness on the blades. However, internal components in the variable pitch system have been interference each other. Electromagnetic interference (EMI) problem have been one of the most serious problem, Variable-pitch wind turbine can not work properly.First of all, the paper analysis the failures of variable-pitch system in the wind mill, and find main sources of interference and interference coupling paths and sensitive equipments, that could affect normal operation.Secondly, measure the grounding resistance of various subsystems in the wind turbine, and measure the ground resistance of DP bus shield in the wind mill. In the laboratory, measure the interference waves of DC bus when servo motor works in different static loads. And then measure the time of charge and discharge in different variable motor speeds, in order to determine the capacity of ultra-capacitor and try to reduce the rates of EMC. Measure the waveform of encoder in the mode of manual and automatic.Finally, compare two variable pitch structures that cause the problem of electromagnetic compatibility, in order to find the best design structure. This article also design the improvement of hardware, redesign the corresponding power supply and EMI filter signal filter, in order to suppress the power grid from the transient interference. And design multi-level surge protection of AC power, to resolve the wind turbine system of variable pitch system by electromagnetic interference after the transmission lines. The paper also changes the PLC software that controls the blade speeds, in order to reduce the frequency of pitch and the problems of electromagnetic compatibility. But the improvement of variable-pitch system could test in the wind mill.