Research Of Permanent Magnet Wind Power Control System And Low Voltage Ride-Through

As the development of human society, the requirement of resources is largerand larger. But in the modern world, the capacity of non-renewable resources,such as coal and oil, is becoming less and less. There will be a big impact in oursocial life if we still do not take any necessary measure. Wind power, as a kind ofrenewable resources, don’t need to be worried about the problem of resourceexhaustion, and it will not cause the environment pollution. So how to use thewind power is becoming the research focus for many countries. Among the windpower technology, the wind power generation, which is seen as a new powergeneration technology, is very promising.The permanent magnet direct drive wind power generation system is usedfor researching after analysis and compare in this paper. But the electrical energyfrom the generator cannot directly connect to the grid because the wind power,which is captured by the wind turbine, is not stable. So in this paper, it takes thecontrol method of rectifier and inverter to make the electrical energy from thegenerator meet the conditions of grid-connectted. The control goal of rectifier isto capture the maximum wind power in this paper, and it sets up a model of speedouter-loop and current inner-loop. The control goal of inverter is to ensure theDC voltage stability and to keep the output reactive power for0, then it sets up amodel of voltage outer-loop and current inner-loop. The SVPWM is used both inrectifier and in inverter to output trigger pulse, which can control the IGBTclosed or disconnect.And then this paper analyses the condition of symmetric failure. Accordingthe characteristic of DC voltage will increase at this time, it introduces twomethods to achieve low voltage ride-through. The first one is to set up a damp load protect circuit by the side of DC, which can consume the redundant DCpower. The second method is to set up a protect circuit for reducing the outputpower by the side of motor, which can make the active power by the side ofmotor equal to the active power by the side of grid. The two methods are bothautomatic switching when the grid happens failure, which can achieve thepurpose of keeping DC voltage stable through the switch control. When the gridhappens asymmetric failure, the negative sequence voltage, the negativesequence current and2harmonic power will come out. It also can achieve thepurpose of low voltage ride-through by building a corresponding control model.Finally this paper sets up the simulation model of the whole control systemand low voltage ride-through based on Simulink, which can verify theeffectiveness of the proposed control strategy.