New current controller for inverter fed medium voltage drives with LC filter

In high power medium voltage drives, the switching frequency of power semiconductor devices is restricted because of high switching losses. Such drives often include an LC output filter, introducing a resonant circuit that may be excited for instance by fast control transients. One way to avoid such oscillations is using damping control schemes, which in turn usually require switching frequencies well above the filter resonance. This paper proposes a new predictive stator current controller that avoids the excitation of the filter resonance, performs active damping and allows fast current control while maintaining low switching frequency. Simulation results of a 2.4 kV induction motor drive and experimental results obtained from a 55 kW prototype a.c. drive demonstrate feasibility and good dynamic performance of the proposed control approach.