Study On AC Excited Wind-Energy Generation System Fed By Matrix Converter

Utilizing wind-energy as clean energy is behave of human society progress and the expression of environmental conservation concept. The most perfect scheme of utilizing wind-energy is to transform wind-energy to electric-energy and then send it to the mains. As the best technical scheme at the present time, AC excited generator is used for wind-energy generation with variable-speed and constant-frequency. Because it operates in large range of speed and with the best utilization factor of wind-energy, the system becomes direction for wind-energy generation. From point of view of electric-energy control, AC excited generation system for wind-energy with variable-speed and constant-frequency includes AC excited generator, AC exciter and the control system. The thesis studies the mathematical model of AC excited generator and its relation of power transfer, steady operation characteristics, capability of over-load and stability of excited generator in synchronous and asynchronous mode, control strategy of matrix converter as AC exciter and the performance of control system for wind-energy generation with variable-speed and constant frequency AC generator excited by matrix converter. The conclusions are as follows: 1. The mathematical model of AC excited generator based space vector is presented, the transfer relation of real and reactive power between stator and rotor is derived and so the control rule on real and reactive power of the generator is developed from the new point. 2. Real power-angle and reactive power-angle characteristics of AC excited generator in synchronous mode are derived. As a consequence, steady operating area of static state, "U"curve for relation between stator and rotor current and real and reactive power from stator, and vector diagram for different operating states of the generator are drawn. These results present a new method for analysis of static performance of AC excited generator in synchronous mode. 3. Expression of electromagnetic torque of AC excited generator in asynchronous mode is derived. The analysis to the torque characteristics shows that AC excited generator can work in asynchronous mode without power-angle limit of stabilization and has the strong capability of over-load. 4. SPWM control strategy and design for voltage-source matrix converter are found which requires simple control and less calculation for switching function. Experiments on a prototype are conducted to verify the design. 5. Current followed control technique is applied in the current-source matrix converter。Design and prototype are made. Result of experiments shows that the matrix converter on this scheme has rapid dynamic response, amplitude, frequency and waveform of its output current are coincide with the setting, and its current waveform is almost sinusoidal. 6. Output power of AC excited generator is controlled by the control strategy oriented to the stator flux-linkage. An algorithm is derived to control independently stator real and reactive power of AC generator by respective two components of exciting current fed in the rotor. Voltage-source matrix converter is used as AC exciter to feed the rotor and a decoupling control mode for exited circuit is adopted. And then control model is constructed and simulated for AC excited generation system for wind-energy with variable-speed and constant-frequency that has the best utilization factor of wind-energy. The result of simulation show the system has excellent performance for wind-energy generation with varying-speed.