Research On Fault Ride Through And Control Strategy Of The Direct Driven Permanent Magnet Synchronous Wind Turbine Generators

Looking over the current state of wind power in China, wind power consumption has become a crucial obstacle to wind power development recently due toproblems such as self-regulating ability of the electricity network in some windy areas and controllability of wind farm while integrated to the electricity network. However,both self-regulating ability of the electricity network and controllability of wind farm should be improved so as to increase the penetration of wind power into electricity network.Controllability of wind power mainly depends on grid adaptability of wind turbine generators (WTGs). Generally, grid adaptability of WTGs includes many aspects, such as active power control and grid frequency response, reactive power control and support capability to grid voltage fluctuations, fault ride through capability and support to grid recovery, power quality immersed from wind farm and etc. Among them, fault ride through capability and related support capability to grid recovery has been considered as the most challenging and important technical indicators as they are closely related to the stability of electricity network.This paper summed up the crucial technical issues and coming technical challenges about the grid fault ride through capability of permanent magnet synchronous wind turbine generators (D-PMSG) based on the analysis of diverse grid codes and practical research, development and engineering experiences. Meanwhile,the important problems that are tightly related to fault ride through capability of D-PMSG, such as hardware scheme of D-PMSG, topology of full power converter and transient characteristics of D-PMSG during gridfault, have been studied,D-PMSG fault ride through solutions have been discussed. Afterwards, the mathematical modeling of D-PMSG and equivalent simulation model of D-PMSG have been realized on PSCAD software platform. Lastly, the new control strategies for voltage ride through and frequency ride through schemes of D-PMSG have been realized, corresponding simulations and real tests have been executed to verify the correctness of the proposed methods in this paper, these results also showed good grid adaptability (all of the mentioned grid codes are satisfied) of D-PMSG about grid fault ride through capability.The new method about the active power controllability of D-PMSG mentioned in this paper integrates the core thoughts of some of the existing methods, such as maximum power point tracing (MPPT), inertia response control (IRC) and pitch control (PT). Inertial control response of D-PMSG and primary frequency control response of wind power plant will be valuable methods if required by electricity network operators, this method also brings some advantages to increase penetration ratio of wind power on the electricity network side. The research achievements have valuable theoretical and practical significance.The optimized method about voltage ride through (VRT) capability of D-PMSG mentioned in this paper also integrates the core thoughts of some of the existing methods, meanwhile the requirements of international grid codes have also been considered. The VRT response of D-PMSG will be a valuable method if required by electricity network operators or international customers. The research achievements have valuable theoretical and practical significance, it isalso helpful to export D-PMSGs to international market.