A Study Of Variable Speed Constant Frequency Doubly Fed Wind Power Generation System And Its Excitation Control Strategies

As one of the most important renewable energy, wind power is of significance in alleviating the world's energy crisis and environmental crisis, and has attracted a great attention around the world. With the development of high-efficiency and high-capacity for wind turbine, variable speed constant frequency (VSCF) doubly fed wind power generation system becomes the main trend of nowadays wind power generation technology for its advantages of its inverter with small size, light weight, low cost and high efficiency. The pitch-controlled wind turbine for maximal wind energy capturing and VSCF has now become the most important technology, so studying of excitation control technology for VSCF doubly-fed wind power system is necessary.In this paper, VSCF doubly-fed wind power system was adopted and conducted a depth study from simulation to test and from theory to practice based on concluding the technologies of VSCF at home and abroad. First, the operating principle of VSCF doubly-fed wind power system is analyzed, its equivalent circuit diagram is established, the mathematical model under the dq synchronously rotating reference frame are established, the power characteristics of VSCF doubly-fed wind power system are analyzed and a new power relationship is also mentioned. Secondly, based on the theory of VSCF doubly-fed wind power system, stator flux oriented vector control strategy and direct power control strategy have been studied and compared in detailed, then the linear optimal control strategy was proposed to VSCF doubly-fed wind power system for its better dynamic stability and transient stability. Thirdly, taking Matlab/Simulink as a platform, a single-machine infinite-bus system simulation model of VSCF doubly-fed wind power system is established, and with this model of VSCF, the simulation has been worked on the linear optimal control strategy. At last, a small-capacity generating units was built to simulate VSCF wind power in the laboratory, in which the main equipment parameters of excitation system are designed and the basic parameters of the rotor were measured for the next test.