关键词: T型中点箝位, 控制算法, 下垂控制, 中点电压, 平衡控制

Abstract: Aiming at the problems of control system failure caused by point voltage offset of three-level TNPC inverter, excessive THD of network measurement current and load mutation over loss control during inverter, a new control algorithm strategy of three-level TNPC converter was proposed and verified by simulation experiment. The simulation verified the correctness of TNPC converter control strategies such as droop, voltage-current double closed-loop and midpoint voltage balance. Through the simulation waveform, it was concluded that the output voltage of DC side and the current of grid side met the requirements when rated load, and the current THD<3%, which met the requirements of national standards. When the load was suddenly changed (from 100% rated load to 30% load), the DC side voltage increased in a certain range and finally reached stability. When the load mutation was stable, the THD of the network side current was analyzed by FFT, and all indicators met the requirements.

Key words: T-type neutral point clamped(TNPC), control algorithm, droop control, midpoint voltage, balance control