Patent ID: 6151227
Filing Date: 2000-11-21
Classification: H02M

Abstract:
A controller for a power converter comprising:n converters which convert DC power to AC power, n being an integer greater than 1, each of which includes bridge-connecting self-extinguishing type switching elements, and feedback diodes which are respectively connected to each said self-extinguishing type switching element,n transformers for respectively inputting the outputs of said n number converters, and connecting with an AC load by connecting in series the secondary sides of said n number transformers, and being provided with:means for providing a voltage command vector of an AC output voltage of said power converter;means for providing all output vectors of said AC output voltages which said power converter can generate;output vector selection means for selecting said output vectors according to said voltage command vector; andcontrol means for controlling conductive states of said self-extinguishing type switching elements according to output vectors selected by said output vector selection means,wherein a spatial vector diagram is split into 6 ranges: 30 degrees, 30 degrees to 90 degrees, 90 degrees to 150 degrees, 150 degrees to 210 degrees, 210 degrees to 270 degrees and 270 degrees to 330 degrees, and range numbers 0 to 5 are assigned to those 6 split ranges,said output vector selection means comprising:(a) a calculate means for calculating said range number in which said voltage command vector is present;(b) a rotate means for rotating said voltage command vector through a specified angle;(c) a coordinate convert means for performing coordinate transformation of said rotated voltage command vector to a vector in an oblique coordinate system which takes a first vector in the -30 degrees direction and a second vector in the 30 degrees direction of the rectangular coordinate system as two unit vectors;(d) a split means for splitting a converter output-enabled portion of said vector diagram, which has undergone oblique transformation, using said unit vectors of said -30 degrees to +30 degrees range, of a spatial vector diagram in which said output vector is positioned, into square-shape patterns so that said output vector is positioned either in an upper left, a lower right, or both said lower left and upper right of each square-shape pattern, and then splitting any square-shape pattern which holds said output vector in both said lower left and said upper right, into two triangular domains by a segment which joins an upper left vertex and a lower right vertex;(e) a judge means for judging whether said voltage command vector which has undergone oblique coordinate transformation is present in either said square-shape pattern domain or said triangular domain in said oblique coordinate system diagram which has been split into said domains; and(f) a select means for selecting said output vector corresponding to said square-shape pattern domain or said triangular domain according to results of said judgement; and(g) a calculation means for calculating an output vector which is rotated through a specified angle as said selected output vector.