Under the balanced or unbalanced grid voltage, the PWM voltage source rectifiers should have many advantages such as sinusoidal input current, unity power factor, four-quadrant operation, the DC voltage stability, etc., so it can be employed in very broad application field. When there is only fundamental positive sequence current component in AC current, the voltage in DC side will remain constant, the rectifier will achieve efficient transformation of power quality. It is necessary to start from control strategies to eliminate harmful components such as the negative sequence current, to improve power quality in rectifier transformation. The mathematical model of PWM rectifier under unbalanced grid voltage was established in the synchronous rotating coordinate system in this paper. The simulation studies of rectifier under unbalanced grid voltage were conducted

In order to deeply understand the characteristics of the permanent magnet synchronous motor direct torque control method, its mathematical models were established in the two-phase stationary coordinate system, the two-phase synchronous rotating coordinate system, and x-y stator synchronous rotating coordinate system. The implementation process of direct torque control method in varied stator winding connection was analyzed in detail. In order to improve the speed and torque performance of the permanent magnet synchronous motor, the direct torque control block diagram and the space voltage vector selection table were given. Finally, the summary and outlook of reducing torque ripple in the permanent magnet synchronous motor direct torque control methods.

In order to make wind power generation system connect to the grid normally in the grid voltage transient fault, it is required in grid security standards that wind power generation system has some capability of fault run-through. The nonlinear controller was designed based on feedback linearization technique. The controller's main purpose is to improve the wind power system steady state performance while to gain better dynamic response speed via controlling the motor terminal voltage and rotor rotation angle. Simulation results indicated that the proposed method could improve the dynamic response speed, as well as improve the steady performance of the wind power generation system.

Aircraft anti-skid braking system providing protection for the safety of the aircraft landed by controlling the brake pressure to be maintained slip ratio in best condition. The aircraft anti-skid braking system is hard to control as the nonlinear model of the aircraft dynamics, the uncertainty of friction between the tires and the ground of braking process. With the study of slip ratio and research of aircraft anti-skid braking system dynamics model, the sliding mode variable structure controller is designed. Then index reaching law is adopted to eliminate the system chattering and the performance is analyzed, further more the robustness is strengthen. Simulation results indicate that: the slip ratio follows the optimum slip ratio, the input signal is smooth, achieve the purpose.

The paper analyzed the composition of the aircraft synchronous generator system. The simulation model of the three-stage synchronous generator is established in the environmental of MATALB according to the motion equation of generator and coordinate transformation. Proposed a control algorithm based on the Sliding-mode Variable Structure Control (SVSC) theory after analyzed the conventional control algorithm of voltage regulator. Particularized the realized method of the SVSC algorithm is proposed. Simulation of both control algorithms were conducted under MATLAB. Simulation results indicated the validity of the SVSC algorithm and advantages against conventional control algorithm.