The Research On Power Converter And Its Control Strategy For Direct-drive Wind Power System

As is known to all, the wind is everywhere, ever-present, will not disappear with the passage of time, so the wind is a kind of renewable energy, has immeasurable potential value. So the large volume wind farm and building large wind power system is very necessary. Random the progress of science and technology, all kinds of wind power system has been built and put into production operation, in the wind power system model VSCF obtained the recognition of people, also gradually replace the existing power generation system and become the best. Direct drive wind power system adopts low speed of PMSG, without gear box, improve the trustly of the unit, reducing the rumble. For the permanent magnet motor rotor structure, unnecessary by the excitation power supply for excitation, so its high efficiency, long life, light in weight. So the direct drive wind power system has become one of the trends of future wind power development. And this article is on the basis of many scholars studies to converter in direct drive wind power system and its corresponding control strategy is studied. This topic has done the main work is summarized as the following several aspects:Compared and analyzed different types of wind power systems, reviewed several kinds of commonly used wind power system, given the topology structure 、same and different places 、 generator types 、 respective advantages and disadvantages and applicable range of them. Compared and analyzed direct-drive PMSG system and constant speed constant frequency SCIG system. Finally discussed the development trend of wind power generation system and the work emphasis in the future. It has certain reference value for research and choose of wind power system.In order to learn more about the system and meet the needs of experimental emulation, the components of direct drive wind power system have been deduced mathematical formula, its mathematical model is established, including the mathematical model of the wind turbine, drive chain mathematical model, the mathematical model of the permanent magnet synchronous generator, inverter mathematical model, etc.The paper carried a in-depth study on the power converter of 1.2 MW DVSCF wind turbine, put forward a scheme of the converter which is applicable to the system, the topology of converter adopts uncontrollable rectifier+Boost converter circuit +SPWM inverter circuit. The original single Boost converter is improved, and put forward the multiple parallel Boost converter circuit, over-voltage protection circuit has been added to the circuit, the system state equation and control strategy are given, and the circuit of the input current ripple is analyzed. The paper also studied several kinds of typical MPPT control algorithm, which are maximum power point tracking control whic are based on the power curve, maximum power point tracking control that according to the optimal tip speed ratio, maximum power point tracking control according to the optimal torque and maximum power point tracking control based on climbing the mountain search. Based on the original mountain climbing searching algorithm the paper proposed a new kind of mountain climbing algorithm, improved the search speed and the accuracy of maximum power. Considering the characteristics of the 1.2 WM direct-drive turbine unit, the article used the direct current control strategy for the grid side inverter.