Research On Low Voltage Ride-through Technology Of PMSG

In recent years, with the fast development of the clean renewable energy - wind power, the wind power makes up a growing percentage of power grid,the wind power and the grid has a big influence to each other. To maintain stability of the grid and protect the wind generator power when the voltage fluctuations or the voltage drops, each country has established corresponding a set of standards for the technology of low voltage ride through. As one of important directions in the present wind field research ,it's important to study the LVRT of PMSG.This paper establishes the mathematical models of the wind power system, containing the models of wind turbine, permanent magnet synchronous generator and converter at the grid side. This paper studies the PMSG and establishes transient mathematical model of the wind power system. This paper studies the strategy of the double loop at the converter of the grid side ,and analyses the operating principle and realizes the decoupling control of active power and reactive power, and studies three methods of improving the Low Voltage Ride Through : adding a unloading circuit at the side of DC, adding reactive compensation at the side of grid and adding shunt resistance at the side of stator.This paper establish the model of the wind power system in the MATLAB and analysis the simulations. the results of the simulations show that we can control the grid-side converter to realize the decoupling control of the active power and the reactive power and to realize the LVRT of PMSG when the drop range of grid voltage is narrow and the drop time is short; however, the original control system has been unable to achieve the LVRT when the drop range of grid voltage is large and the drop time is long, we should increase other measures to protective the system. This paper establish the other models including adding a unloading circuit at the side of DC, adding reactive compensation at the side of grid and adding shunt resistance at the side of stator, then analysis the simulations. the results of the simulations show that adding a unloading circuit at the side of DC can improve the ability of the LVRT at a certain extent. Combining the unloading circuit at the side of DC with the reactive compensation at the side of grid and Combining the unloading circuit at the side of DC with the shunt resistance at the side of stator can well improve the ability of the LVRT.