Study On Dynamic Simulation Of Doubly-fed Wind Power Generation System

With the depletion of fossil fuels and the requirement of harmonious socialdevelopment, the wind power is as a rich and clean part of natural energy in Chinaand its superiorities are the short infrastructure construction cycle, low cost, highreliability and low loss. However it is difficult to solve related problems of windpower generation because of its complexities. We need to study the staticperformances and transient performances of wind power generation whichdetermine whether the entire system can be operated stably in various conditions.So the software and hardware of system are needed to verify the reliability of theentire system. It is not realistic to mounting the prototype to real installation forwind farm system in the lab and the environment of wind farm could not becontrolled. As the above reasons, a simulative system of the doubly-fed generator isneeded to simulate the complete wind power generation system.Most of the existing simulative system designs are based on steady-stateoutput characteristics of wind turbine. The simulative system in this paper uses thedynamic simulative torque control of prime mover and speed loop and current loopdouble loop control of doubly-fed generator. The studies of static performances andtransient performances take wind shear effect, tower shadow effect,big inertia ofthe actual wind turbine and drive shaft system into account. A dynamic torquecompensation is used to make the dynamic response of the simulative system closerto actual ones and can be studied as actual wind farm system in experiment.The wind shear effect and tower shadow effect result in third harmonicpulsation of the output torque and power. A additional torque control is proposed toreduce the pulsation amplitude of third harmonic power to make the output powersteady. In the situation of grid failure or even short circuit, it also proposes a switchcontrol under the condition of three-phase short circuit, the switch control cangreatly reduce the time and amplitude of the oscillation due to the short-circuitfault of DFIG.Based on theoretical analysis and simulation of the system, a experimentalplatform of a15kW asynchronous motor driving an11kW doubly-fed generator wasconstructed. For the differences of inertia between the wind turbine simulator in laband actual wind power system, this paper uses dynamic torque compensation to simulate the different inertia. On this basis, experimental results show that the windsimulative system can reflect the grid power quality in wind power, systemstabilities of the transient state, steady state and control strategy. Both thesimulation and experimental results confirmed the correctness of wind simulativesystem and control strategy.