High Frequency Pulse Wave Suppression Strategy For Generator Side Converter Of Wind Turbine

During the “Twelfth Five-Year Plan” period,the development of wind power generation entered the scale stage rapidly,but it also accompanied the failure of wind turbine windings and large-area off-grid faults,which seriously endangered the safe and stable operation of the power system.In this paper,the overvoltage problem caused by the PWM(pulse width modulation)high-frequency voltage pulse wave transmitted by the generator-side converter through the long cable line in the wind turbine power generation system is studied,and the generator-side converter current is established.A mathematical model of the long cable drive of the generator-side converter is established,and passive filters and active filtering strategies are designed to suppress the overvoltage of the generator.In order to explore the generator overvoltage generation mechanism,combined with the wind power generation system structure,the rotor-side converter control strategy of the doubly-fed wind power generation system and the generator-side converter control strategy of the permanent magnet direct-drive wind power generation system are analyzed.And establish a mathematical model of the generator-side converter to explore the mechanism of high-frequency pulse voltage wave generation.The equivalent circuit model of the long cable drive system of the converter is established.Combined with the principle of converter high-frequency pulse voltage wave enhancement by long cable reflection,the relationship between cable length,PWM rise time,converter terminal and generator terminal reflection coefficient and overvoltage peak function is derived.The influence of cable structure and cable insulation on the overvoltage of the generator is analyzed.The simulation model of MATLAB/Simulink is used to illustrate the influence of the overvoltage of the terminal on the voltage waveform of the terminal.In order to suppress the over-voltage of the generator and improve the reliability of wind power operation,the suppression effects of four passive filter networks for PWM high-frequency pulse waves are discussed.The transfer function of the derivation filter network is analyzed and the filter parameters are optimized.The effectiveness of four passive filtering networks is verified by MATLAB/Simulink simulation.At the same time,the reliability of the four filters in the suppression of generator overvoltage under the condition of sudden change of system impedance parameters is analyzed.In order to eliminate the interference of system impedance parameters and improve the robustness of the overvoltage suppression of the generator,according to the mechanism of the over-voltage of the generator and the control strategy of the generator-side converter,the generator-side overvoltage suppression strategy with adaptive parameter identification is proposed.Through the simulation analysis of MATLAB/Simulink,the overvoltage suppression effect before and after the additional adaptive control is compared,and the effectiveness,rapidity and robustness of the PWM high-frequency pulse wave adaptive suppression strategy are verified.