The Research Of Direct Torque Control For Generation-side Converter Of Permanent Magnet Direct-drive Wind Power System

With the rapid economic development,energy consumption increased year by year,and increasingly serious environmental pollution,wind power has received wide attention of the world.The variable speed constant frequency(VSCF)wind power generation system is currently the most widely used power system.Due to its simple structure,good control performance and high reliability systems,direct drive VSCF wind power generation system has a great advantage in the wind power generation of MW level.In this paper,as a control objective of the generation-side converter of permanent magnet direct-drive wind power generation system,a direct torque control(DTC)method was studied.The structure and working principle of generation-side control system in permanent magnet direct-drive wind power were introduced firstly.We established the mathematical models of permanent magnet synchronous generator(PMSG)in the three-phase stationary coordinate system,the two-phase synchronous rotating coordinate system and the two-phase stationary coordinate system.The basic mathematical model of the machine side converter was deduced.It laid a good theoretical foundation for the follow-up study.We described the DTC theory and gained the basic DTC control thought,and gave a structure of permanent magnet direct-drive wind power system on direct torque control.The control principle of the system was analyed.The chains and torque observation model of direct torque control of PMSG on the oriented stator magnetic fields were constructed.The construction process of switching vector table was explained in details.We also made a simulation about DTC system of PMSG based on switch table.To solve the problem of high torque and flux fluctuations in traditional DTC based on switch table,we put forward some corresponding improvement measures.Firstly,the stator flux observer including the stator resistance compensation correction and the improvement of integral part was improved.We proposed the methods on DTC based on SVPWM and DTC based on predictive SVPWM,and conducted a simulation study on the two kinds of control strategy.The results showed that these improvements could effectively reduce the torque and flux fluctuations.It improved the torque,flux and stator current waveform,and the control performance of the system.Finally,we carried out the hardware design and software design of the direct torque control of direct-driven permanent magnet synchronous generators for wind energy conversion based on the TMS320F2812 chip of TI Company.It will have some guiding significance for the further study.