Harmonic Current Depression for Medium Voltage Three-level Wind Power Converter with Active Damping Control

Medium voltage three-level wind power converter is a good choice for the next generation 10-MW wind turbine. However, since switching frequency of medium voltage semiconductor device is strictly limited, harmonic current is hard to depress, especially for LCL type wind power converter. This paper presents an effective way to eliminate resonance current under low switching frequency. Active damping strategy, instead of passive damping, is adopted here. Detailed system model is built, which shows the converter harmonic terminal voltage, generated by the PWM section, introduces considerable the resonance harmonic current. To guarantee system stability, a negative proportion gain is used in the active damping feedback loop. According to the system model, a low pass filter is also adopted in the converter current feed-back loop, where harmonic current depression performance is greatly improved. Experimental results validate the theoretical analysis.