Patent ID: 9088225
Filing Date: 2015-07-21
Classification: H02M

Abstract:
1. A switching branch for a three-level converter, the switching branch comprising: a first semiconductor switch and a second semiconductor switch connected in series between a positive direct current pole and an alternating current pole of the switching branch; a first diode connected in parallel to the first semiconductor switch, and a second diode connected in parallel to the second semiconductor switch; a third semiconductor switch and a fourth semiconductor switch connected in series between a negative direct current pole and the alternating current pole of the switching branch; a third diode connected in parallel to the third semiconductor switch, and a fourth diode connected in parallel to the fourth semiconductor switch; a fifth semiconductor switch connected between a neutral direct current pole and a connection point between the first and second semiconductor switches; a sixth semiconductor switch connected between the neutral direct current pole and a connection point between the third and fourth semiconductor switches; a fifth diode connected in parallel to the fifth semiconductor switch, and a sixth diode connected in parallel to the sixth semiconductor switch; and a control arrangement for controlling the semiconductor switches, wherein the first semiconductor switch, the first diode, the fifth semiconductor switch and the fifth diode reside in a first switching branch-specific semiconductor module, wherein the fourth semiconductor switch, the fourth diode, the sixth semiconductor switch and the sixth diode reside in a second switching branch-specific semiconductor module, and wherein the control arrangement is configured to perform at least one of: control each semiconductor switch, when the converter operates as a rectifier, such that when a first current flows into the switching branch through the alternating current pole, said first current always flows through either the first diode or the fifth semiconductor switch, and such that when a second current flows out of the switching branch through the alternating current pole, said second current always flows through either the fourth diode or the sixth semiconductor switch; and control each semiconductor switch, when the converter operates as an inverter, such that when a first current flows into the switching branch through the alternating current pole, said first current always flows through either the sixth diode or the fourth semiconductor switch, and such that when a second current flows out of the switching branch through the alternating current pole, said second current always flows through either the fifth diode or the first semiconductor switch.