Search Of Double-fed Machine Variable Speed System Based On DSP

Double-fed variable speed system (DVSS) is a kind of variable speed drive system handled by rotor AC excitation, which are composed of machines and AC excitation control systems. Compared with the ordinary variable speed drives with single fed induction machines, it has many advantages such as small capacity, low voltage, adjustable power factor, low price of technical reconstruction and good variable speed factor. DVSS could be widely used in industry area.Firstly, according to the basic principle of electrical machine, the Double-fed machines (DFM) mathematical model in the synchronous M - T reference frame is established. The interrelations of key physical parameters such as power,electromagnetic torque are discussed。Based on above results ,AC excitation's control effect to stator current and rotor current, DFM's operational characteristics and power analyzed. It concludes that, stator current can be easily separated into torque part and excitation part, control of rotate speed and power factor can be decoupled by adjusting rotor AC excitation based on stator flux oriented vector control strategy.In this thesis, dual close loop control structure is adopted to DVSS. The rotor speed and the power factor of stator side are defined as object function of outer loop. The current of the rotor is defined as object function of inner loop. The rotor speed and the stator power factor is controlled by the rotor currency.Combining with DSP and AC/DC/AC converter technology, we also set up a small power DVSS experimental platform with a 380v/11kw fan- motor group. Experimental results are in accord with analyses in theory , and anticipative purpose is arrived.