Direct controls in voltage-source converters - generalizations and deep study

The well-known principle of the direct torque control applied mainly to squirrel-cage induction motor drives can be generalized and applied to other machines, quantities, converters and systems. These are: other AC machines (double-fed induction and permanent magnet synchronous machine), active and reactive power, direct power control of the line side converter, direct controls of both of the converters in a DC link inverter. The idea is the same for all of them and can be generalized. Looking deeper into the operation of the direct controls, some special effects can be found: different resulting error bands and switching frequency in different operation modes of the converter, large delay in reference tracking. These can badly affect the operation of the control: larger (not the expected) error, larger switching frequency, slower control. Methods are given against them: modified switching tables, increasing the number of sectors, selecting proper sector orientation.