A fixed point variable sample rate frequency adaptive bandpass filter for extraction of synchronization information from AC utility network signals

This paper presents design procedures for two adaptive bandpass filters with variable sample rates and fixed point implementations. Each bandpass filter can be used as an integral part of a multirate phase lock loop (MPLL) for extracting the fundamental component from an input signal. The MPLL provides synchronization information from zero crossings of power system AC signals. The MPLL incorporates frequency adaptation intrinsically by generating a sample signal which is an integer multiple of the fundamental frequency component. The integer multiple frequency is used as a sampling signal for all signal processing/filtering blocks within the MPLL. The bandpass filter ensures that the MPLL is robust against disturbances that appear on the power system. Finite impulse response (FIR) and infinite impulse response (IIR) architectures are studied for the design of bandpass filters. The FIR architecture offers unconditional stability and ease of implementation and hence is selected for the MPLL. The FIR filter is implemented on a Xilinx field programmable gate array