Study On Lightning Transient Simulation Of Wind Turbine Generator System

In recent ten years, with the increase of wind turbine generators installed capacity and wind farm dimension, the safe and reliable operation of wind turbine generators is more and more important. According to IEC/TR61400-24data promulgated by the International Electro technical Commission shows:Lightning activities are frequent in Sweden and Denmark which are Northern European countries, the lightning damage rate of each hundred wind turbine generators remains about4%～8%. However, the damage rates of wind farms in some areas of our country are greater than the value. As the actual factor of influencing wind turbine generator security operation, lightning disasters of wind generators has been concerned a lot.The purpose of the dissertation is to study lightning transient process, establish the model of wind generators, and calculate current distribution and harmful degree of lightning overvoltage quantitatively in different parts of tower, when wind turbine generator is struck by lightning. The research provides quantitative indexes and reliable references in order to lightning protection design of wind turbine generators. What s more, it can guide lightning protection personnel to take corresponding measures to lightning protection.When wind generators is struck by lightning, the powerful lightning current often injects the blade tip of wind turbine generators and flows through inner conductor to blade root. Then lightning current flows through the main shaft, bearing and nacelle conducting path to the top of tower and injects into the grounding system of tower foundation which is finally dissipated into the ground. This thesis introduces detailedly that how to build calculation model of lightning discharge, blade, nacelle, tower and grounding device, and how to convert the whole conducting path into an electric network composed of series of π type circuits.Because of using "wire grid network model" to divide tower, the relative position of equivalent conductors in the space are complex, What s more, there are few paper reporting at home and abroad about electrical parameters calculation between conductors in relative complex positions in the space. Therefore, this paper puts emphasis on deducing electric parameters (inductance and capacitance) calculation formulas of sloping conductors. There are programs of calculating electric parameters of conductors using MATLAB software in this paper, put the data of electric parameters into the Electric Magnetic Transient Program software, and then use EMTP to simulate lightning transient process of wind turbine generators. Current distribution and voltage lifting of blade, bearing, nacelle, tower and grounding device are calculated separately. In addition, this paper also analyzes influences on transient responses of lightning in different situations, such as current waveform, coupled electric parameters,’wire grid network model division’, the lightning site and grounding resistance.In this paper, there is designing a reduce-size model of an actual wind turbine generator system in laboratory which capacity is2.5MW, and making impulse current generator to simulate lightning current. The experimental results verify models and numerical calculation methods correctly.