Research On Passivity-Based Control Of Brushless Doubly-fed Wind Power Generator

The Brushless Doubly-Fed Machine (BDFM) is a single-frame, self-cascaded induction machine capable of operating in both the induction and the asynchronous mode. BDFM has the robust mechanical characteristics together with controllable power factor, good speed characteristics, a low power converter and diversiform run mode. Therefore it is especially suitable for the AC drive system and variable speed constant frequency(VSCF) generating system.The structure characteristics and principle of BDFM is analyzed, and BDFM simulation model was constructed with MATLAB/Simulink environment. Based on this software platform, the operation modes of BDFM, including single-fed, doubly-fed synchronous, doubly-fed sub-synchronous and doubly-fed super-synchronous, have been simulated, and the machine open-loop characteristic has been analyzed.The dissipativity and passivity of nonlinear system and Euler-Lagrange(EL) function has been introduced. The dissipativity and passivity of EL system is discussed. Design of passivity-based controller is presented by adopting passivity-based control theory. According to the time-variant characteristics parameter, the nonlinearity coupling variables and no easy measuring the rotor current of IM, the EL model of induction machine (IM) were constructed with analyzing the dynamic equations of stator current and rotor flux of IM from the energy viewpoint. A novel improvement control algorithm was proposed with stator current as state variable and no the rotor current observer based on passivity theory. The double-loop passivity-based controller was designed to regulate the speed and torque of IM. The control variables were derived from EL model of IM with substituting by expectation values. From the simulation result, the passivity-based controller was globally stable algorithm which made rotor flux, torque and speed to rapidly track expectation values. The robustness, feasibility and efficiency of the passivity-based controller were verified.Theαβtwo-phase model of BDFM was derived, and its feedback interconnection model was constructed. It was proved that the feedback interconnection model of BDFG(Brushless Doubly-Fed Generator) is passive and it could be decomposed into mechanical subsystem and electrical subsystem. The principle of maximum wind energy capture was expounded with wind power coefficient. By this principle, a new passivity-based speed control system was designed. The simulations results indicated that the rotor speed of BDFG could quickly track the setting value through regulating the voltage of control winding, and it runs good dynamic performance with passivity-based controller. With the controller, the wind turbine could keep running with optimal blade top speed ratio and track the maximum output power below the rated wind speed. The passivity-based controller for BDFG were verified that it is globally asymptotic stabilization without singularity point.