Principles of vector orientation and vector orientated control structures for systems using three-phase AC machines文档.pdf

1 Principles of vector orientation and vector orientated control structures for systems using three-phase AC machines From the principles of electrical engineering it is known that the 3-phase quantities of the 3-phase AC machines can be summarized to complex vectors. These vectors can be represented in Cartesian coordinate systems, which are particularly chosen to suitable render the physical relations of the machines. These are the field-orientated coordinate system for the 3- phase AC drive technology or the grid voltage orientated coordinate system for generator systems. The orientation on a certain vector for modelling and design of the feedback control loops is generally called vector orientation. 1.1 Formation of the space vectors and its vector orientated philosophy The three sinusoidal phase currents isu , isv and isw of a neutral point isolated 3-phase AC machine fulfill the following relation: i t + i t + i t = 0 (1.1) su ( ) sv ( ) sw ( ) Fig. 1.1 Formation of the stator current vector from the phase currents 2 Principles of vector orientation and vector orientated control structures These currents can be combined to a vector i (t) circulating with the s stator frequencyf s (see fig. 1.1). 2 j j 2 i = i t + i t e + i t e with = 2 3 (1.2) s 3 su ( ) sv ( ) sw ( ) The three phase currents now represent the projections of the vector is on the accompanying winding axes. Using this idea to combine other 3- phase quantities, complex