Mw Direct Drive Tri-level Wind Power Back-to-back Control System

With the consumption of fossil energy, the shortage of the non-renewable energy, developping new renewable energy becomes more and more important. Wind power is one important part of many green energie. In wind energy conversion system, the role of the converter is abnormal important. In order to improve the efficiency of resource utilization of wind turbine, lower operating costs, increasing the capacity of single unit and improving grid voltage level are the trend of the wind power development. The topological structure of three-level is in favour of improving the grid voltage, optimizing the grid current and voltage waveform, more likely to achieve low voltage ride through, and is the main topological structure for MW wind power system.This topic mainly researches MW thre-level direct driving type back-to-back wind power control system,which contains the following several aspects:Completes the solutions and calculations of the hardware in the3MW direct driving type three-level back-to-back wind power converter. The calculation presented the topological structure of the converter, and describes the design scheme and the calculation process of each part in the machine side and grid side converter,, including the design of the machine side filter, the design of the grid side filter, the parameter design of dc link, the design of brake units, the design of the snubber circuit, the selection of IGBT module and NPC diode and the design of the discharge resister and pressure resister.To ensure the efficiency of the wind power converter, reducing the loss of the converter is necessary. So in the3MW direct driving type three-level back-to-back wind power converter, the switch loss of converter is calculated and analyzed through the analysis of the converter’s working conditions.In order to fulfill the requirement of low voltage ride through for Wind power converter, the grid side converter control and dc-link circuit are used to realize the reactive power operation mode. The dc-link resister circuit is used to consume the excess energy of the dc side. Meanwhile the grid side converter need to provide reactive current to the grid according to the requirements and the fallen depth of the grid voltage. A matlab model of the grid side converter of the wind power system was built in order to verify the LVRT effectiveness of the reactive power operation mode.This paper proposes a new method of three-level dead-time compensation which takes both the dead time and switch delay time into account, and considers the influence of the voltage drop of devices. Two methods of the three level technology are completed based on FPGA:One is building the SOPC system in FPGA to realize the three level technology; Another one is DSP+FPGAmode in which DSP completes control algorithm and FPGA takes the charge of PWM and the other functions. Finally the experiments which were done in the three-level experimental platfonn and South Korea Seoho’s three-level inverter proves the validity and the correctness of the study.