双脉冲测试方法在中点钳位三电平逆变器中的应用研究

Research on Dynamic Voltage Unbalance of Inner and Outer Switch in NPC Three Level Circuit Test

双脉冲测试已成为两电平逆变电路标准的测试方法,将其直接扩展至中点钳位(NPC)三电平逆变器的测试中,会引起内外管动态电压不均衡的问题。本文采用半桥结构的NPC三电平测试电路,并结合两种典型的吸收电路,通过分析状态转换过程,分析了内外管产生动态电压不均衡的电路机理,并指出这种电压不均衡现象是由于传统双脉冲方式无法正确对内外管电压状态进行有效配置而造成的。本文采用一种简单的三管动作双脉冲测试方法,避免了电压不均衡现象的发生。该方法考虑了开关管的死区时间,可以很好对NPC三电平电路中功率器件的瞬态特性及吸收电路的吸收效果进行测试。最后,通过仿真与实验证明了理论分析的正确性及测试方法的合理性。

The double pulse test that is a standard mean in two level inverter is used in the NPC three level inverter,while the problem of voltage unbalance between inner and outer switchs is arisen.Based on three-level half bridge chopper circuit with two different snubbes.The state transition process is analyzied,and the circuit mechanism of voltage unbalance is explained.The reason of voltage unbalance is that the voltage of inner and outer could not be properly configured under the conventional double pulse pattern.The double pulse mean with three-switch action is adopted,and the dynamic voltage unbalance between the inner and outer switchs in conventional test is fully avoided.At the same time,the dead time of switch is considered in the new pulse pattern,and the transient characteristic of power device and the operation performance of snubber circuit can be perfectly tested.The simulation and experimental results show that the theory analysis is right and the proposed test method is rational for testing NPC three level circuit.