| 摘要 |
In a converter having a DC intermediate circuit, the first rectifier (SR1) on the input side is controlled to the nominal magnitude value (i*) of a current vector and the second rectifier (SR2) on the output side is controlled to the nominal angle value (wp*) of the current vector. The nominal magnitude and angle values are calculated by a coordinate converter (KW1) from nominal component values (i1*, i2*) for the reactive current and the real current, and are predetermined for the corresponding reference variables (i1**, i2**), in order to control these two orthogonal vector components independently from one another. The nominal component values are formed from their reference variables by means of ramp integrators (INT1, INT2). In order to match the nominal component values to their reference variables as quickly as possible, the integrators are set to a high ramp rate. In this way, at least one of the rectifiers can reach its saturation limits, as a result of which the independent control of the reactive current and the real current can be interfered with. The ramp rate of the two integrators is thus reduced by a corresponding reduction factor (Vf) to a predetermined maximum value when approaching the control voltages (Uf, U alpha ). In order to reduce the ramp time, the ramp rate is reduced linearly until the nominal component value reaches the value of its reference variable. A maximum commutatable intermediate circuit current is calculated from the voltages of the commutation capacitors and the deviation of the nominal magnitude value from this limit value is used on the one hand to reduce the ramp rate of the real current nominal value (i2*) and on the other hand temporarily to increase the reactive current nominal value (i1*) in order to ensure the commutation capability of the second rectifier. In this way, the current vector can be controlled to the value predetermined by the component reference variables in very short ramp times. This is desirable, e.g. for rapid state changes of a rotating field machine (M) connected to the converter. <IMAGE> |
