| 摘要 |
The invention presents a method for controlling a multi-level inverter (1) using a PWM scheme which comprises a sampling time, the inverter (1) comprising an input circuit (2), a DC link (4) in parallel to the input circuit (2) comprising at least two capacitances (24, 26) in series establishing at least three electric potential levels (Vdc+, Vmid, Vcd-), and an output circuit (6) comprising of a plurality of multi-level output phase legs (31, 32, 33) connected in parallel to the DC link (4), each one of which comprising a plurality of switches (36, 38, 40, 42), a number of diodes (37, 39, 41, 43, 48, 50) and a connection (55, 56, 57, 58) to the midpoint (28) between two of the DC link capacitances (24, 26), and connectable to a load (30) such that the load (30) by switching is connected during operation to either of the at least three DC link potential levels (Vdc+, Vmid, Vcd-), wherein for a time sample of the PWM scheme each of the at least two voltages (Vpos, Vneg) at the DC link capacitances (24, 26) is measured and for each of the output phases (R, S, T) a switching duty cycle based on the measured voltages (Vpos, Vneg) is calculated to generate an output voltage (U). The invention further presents a multi-level inverter comprising a control unit (60) designed to execute the presented method. |
