CPC H02M 1/325 (2021.05) [H02J 3/0012 (2020.01); H02J 3/32 (2013.01); H02J 3/381 (2013.01); H02M 1/0009 (2021.05); H02M 7/5387 (2013.01); H02J 2300/24 (2020.01); H02J 2300/28 (2020.01)] | 13 Claims |
1. A method for operating a three-phase inverter on a three-phase load, in particular on an electrical grid, wherein the three-phase inverter has a direct voltage intermediate circuit, at least one three-phase bridge circuit and at least one control unit for controlling the bridge circuit, wherein, in the at least one bridge circuit, at least two power switches per phase are provided, which are connected in series parallel to the direct voltage intermediate circuit, wherein in the method, depending on predefined target voltage values of the three phases of the inverter, the power switches of each individual phase are actuated via the control unit such that a three-phase alternating voltage is generated on the three-phase load via switching operations of the power switches, wherein a monitoring of the power switches in the individual phases for an overload state is carried out using monitoring means, wherein if an overload state is detected in one or two phases of the three-phase inverter, the bridge circuit continues to be operated with one or two non-overloaded phases at least for the duration of the detected overload state,
characterised in that
instead of the predefined target voltage values, modified target voltage values are determined at least for the duration of the overload state, which are used to control the bridge circuit and, in order to determine the modified target voltage values, the predefined target voltage values of the three phases are transformed into a predefined target voltage rotating phasor in the αβ-coordinate system, the target voltage rotating phasor is decomposed into a differential voltage rotating phasor and at least one modified target voltage rotating phasor in the αβ-coordinate system, wherein the at least one modified target voltage rotating phasor in the overloaded phases takes into account in each case the resulting maximum phase voltage and from the modified target voltage rotating phasor in the αβ-coordinate system, the modified target voltage values can be determined.
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