System and method for soft switching of gate turn-off thyristors in a three-phase, three-level voltage inverter

Abstract

The subject of the application is a system and method for soft switching of turn-off thyristors of a three-phase, three-level voltage inverter having three connection systems, identical for each phase, wherein all main turn-off thyristors (T11, T12, T13, T14 for phase A, T21, T22, T23, T24 for phase B and T31, T32, T33, T34 for phase C) are equipped with soft switching systems, each of which includes an auxiliary SCR thyristor (T11a, T12a, T13a, T14a for phase A, T21a, T22a, T23a, T24a for phase B and T31a, T32a, T33a, T34a for phase C), one capacitor (C11, C12, C13, C14 for phase A, C21, C22, C23, C24 for phase B and C31, T32, T33, T34 ... C32, C33, C34 for phase C). The anodes of the first main turn-off thyristors (T11, T21, T31) are connected to the positive terminal of the inverter power source, the cathodes of which are connected to the ends of the first inductive chokes (L11, L21, L31). The ends of the first capacitors (C11, C21, C31) are also connected to the positive terminal of the power source.The second ends of the first chokes are connected to the anodes of the second turn-off main thyristors (T12, T22, T32), the cathodes of which are connected to the receiver terminals (A, B, C), and the cathodes of these thyristors are connected to the anodes of the third main thyristors (T13, T23, T33). The cathodes of these thyristors are connected to the fourth inductive chokes (L14, L24, L34), the second ends of which are connected to the anodes of the fourth main thyristors (T 14, T24, T34), the cathodes of which are connected to the negative terminal of the power source. Each main thyristor has a capacitor connected via a diode (D11, D12, D13, D14 for phase A, D21, D22, D23, D24 for phase B and D31, D32, D33, D34 for phase C), and one auxiliary SCR thyristor is connected to each capacitor.