| 摘要 |
PROBLEM TO BE SOLVED: To suppress variation of the neutral point potential steadily by reducing the operation load in a multilevel power converter.SOLUTION: Based on the switching patterns V3, V4, V5 affecting a first neutral point potential, voltage command values V=Vu, Vv, Vw, output current detection values I=Iu, Iv, Iw and the discharge conditions of capacitors C1, C2 connected with a second neutral point NP', a neutral point current estimate I^is calculated. A voltage offset component Vis calculated by adding a value obtained by multiplying the neutral point current estimate I^by a first transfer function F(s), and a value obtained by multiplying the deviation of a voltage between the positive electrode of a DC voltage source Vand the first neutral point NP from the voltage between the negative electrode of the DC voltage source Vand the first neutral point NP by a second transfer function G(s), and then a voltage command value is corrected by adding the voltage offset component Vto the voltage command values V=Vu, Vv, Vw. |
