| With the energy crisis and environment issue becoming even worse, more attentions have been turned to the clean and renewable energy source. As the representative of new energy sources, the wind power energy has gained more attention and development. The nowadays commonly used high power wind turbines are suitable for the areas on the sea or where wind energy resources are rich. However in the central and eastern areas of China, the wind energy concentration is poor. The large power wind turbines will impact the grid greatly, in the consequence of the volatility of the generating units. And the low power wind turbines’ efficiency is too poor. Therefore with the concept of micro-grid being put forward, the high efficiency medium wind power turbines has been the center of the research.The efficiency of wind energy conversion is an important target for the wind turbine designing. The wind turbines are consist of wind wheels, generators, converters and control systems. The efficiency of the converter has a direct influence on the overall efficiency. For the sake of improving the efficiency, this paper optimizes the designing of the topological structure, the modulation algorithm and the main circuit parameter configuration. In this paper, the aim of the research is the design and efficiency optimization of medium power converter in wind power system. The main research contents and innovative point are as follows:First of all, the common topologies used in medium wind power converter are analyzed. And for the purpose of optimizing its efficiency, the back-to-back NPC three-level topology is chosen, after comparing the advantages and disadvantages of the diffident topologies (especially the two-level and the three-level topologies).Secondly, the operation principle and modulation method for the NPC converter are analyzed. And for the purpose of reducing the switching loss, the vector sending sequence is optimized. What’s more the research of SVPWM and neutral voltage balance issue are also covered.Thirdly, the mathematical models of the NPC three level converter in the abc and dq :oordinates are deduced. Basing on the models, the closed-loop control systems lor both gna siae and motor side are designed, and the PLL is also covered.With the help of the models, the closed-loop control methods for grid side, motor side, and the PLL are designed.Fourthly, the working principle and designing method of the main circuit (including the power module, the LCL filter and the DC bus capacitance) are analyzed. What’s more, a main circuit parameters configuration method is proposed after researching the loss of the IGBT and LCL filter.Fifthly, after analyzed the drive and protection requirements of the NPC three-level converter, the actual drive circuit based on the2SC0435T is configured.Finally, the construction of the50kW three-level converter experimental platform and the design of the distributed control system based on DSP&FPG A are introduced. And the systematic design and efficiency optimization research are validated with the help of the whole experimental system. |
