V. Moreno, A. Pigazo, R.I. Diego, J. Barros, and E. Pérez (Spain)
Harmonic compensation, digital signal processing, Kalman filtering, active power filter, voltage source converter (VSC), PWM inverter.
The digital control of a VSC-based active power filter must generate the power converter reference current in real time. This current is composed of the non-active component absorbed by the non-linear AC load and a percentage of the active component to compensate PWM inverter losses. Time delays in signal acquisition, processing and reference current generation will cause incorrect harmonic compensation. This cancellation error will depend on the sampling frequency and the current harmonic order to be cancelled. This paper presents a predictive method based on a recursive Kalman filtering algorithm to obtain the current reference of a shunt power filter in real-time. The predictive digital Kalman filter generates the best estimation of the control signal one sample in advance and before the end of the sampling interval. Therefore delays due to acquisition and processing times are corrected. The proposed method improves existing techniques by offering the capacity to adapt in real-time to the characteristics of the current consumed by the non-linear load. The effectiveness of the compensation is optimal and the dynamic response is good under time-variant current harmonics. Stationary and transient responses obtained in a laboratory prototype with this control method are shown. Obtained results using a predictive digital Kalman filter and a non-predictive one are compared.
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