In the wind power converter with multiple level topological structures

three-level neutral-pointclamped（NPC）converter is a promising multilevel topology in offshore megawatt wind power generation systems. However

with the growing requirements by grid adaptability

the requirement to the reliability of converter becomes a more and more high. In view of this issue

in this paper

the thermal load distribution a megawatt three-level NPC wind power inverter in the low-voltage ride-through（LVRT）is analyzed.Then

a kind of improved method for space vector modulation is proposed and related test is designed

under which the thermal load of each power element is redistributed. It is shown by the test result that under the action of new modulation strategy

the thermal load of each power element at low voltage ride through of converter tends to balance

the temperature of power element with maximum stress is also within normal range. This method

at the time of changing thermal load

also increase the control ability to the neutral point potential and this is one of the key techniques of the neutral point clamped topology.