Implementation of a synchronous signal generator with 4th order filter

Abstract

In power electronics systems, synchronization errors degrade system performance. In the past, synchronization methods using a master-slave structure were mainly used, and synchronization errors occurred due to the inherent structure. Therefore, a synchronization structure that shares external analog signals in parallel is proposed. For the implementation of such a system, the implementation of a synchronous signal generator is essential. Therefore, this paper describes the implementation of a synchronous signal generator with a 4th order filter. The main parts of the synchronous signal generator are the 4th filter and the signal maintenance system. The 4th filter functions as an orthogonal signal generator (OSG) and a band-pass filter. The OSG is used to estimate the phase angle, and the band-pass filter is used to cut off the high and low frequency components. A 4th filter was selected because a conventional second order generalized integrator (SOGI) has a problem of not being able to DC reject a 90-degree phase delay signal. The 4th order filter is based on the principle of RLC resonant circuit, and a general expression is derived. In the case of the signal maintenance system, it is a system that continuously generates a synchronous signal using the past signal when the external shared signal is not received due to an accident. The signal maintenance system is included in the 4th order filter in the implementation. Several digital implementations of the 4th order filter have been discussed. The best method was selected by comparing z-transformation distortion (ZTD) and pole-zero map. The synchronous signal generator was implemented using a Field-programmable gate array (FPGA). The hardware design and simulation were performed using Vitis model composer based on simulink provided by Xilinx. The band-pass filter and OSG of the designed 4th filter were verified using signals with high frequency and DC offset as input. Also, the phase following in case of accident with and without signal maintenance system was compared and the superiority was shown through hardware co-simulation.