Predictive Stator Current Control For Three-Level Voltage-Source Inverters With Output LC-Filters

In high power medium voltage drives the switching frequency of power semiconductor devices is limited because of high switching losses. These drives often consist of a three-level NPC inverter with an LC output filter to protect the motor from harmonics. Application of the filter creates a resonant circuit that may be excited for instance by switching harmonics or control transients. However, state of the art damping control methods require switching frequencies well above the filter resonance. This paper presents improvements to a predictive stator current control method which was recently proposed by the authors. The improvement consists of an optimized definition of the inverter's switching transitions and a control method of the neutral point potential. The predictive stator current controller avoids the excitation of the filter resonance and enables very fast stator current control while maintaining low switching frequency. Simulation results of the proposed current control method with a 2.4 kV induction motor drive model show good dynamic and stationary performance.