Abstract

Single-phase modular impedance measurement unit (IMU) is a promising solution to power system stability analysis. Yet, existing designs only have modularity at the power-stage level other than the control-platform level, which restricts the scalability of modular IMUs. As such, this article proposes a distributed communication and control system (DCCS) for high-frequency large-scale modular IMUs with tight synchronization and low latency to enhance the controller-level modularity and scalability. The new architecture is realized on a widely adopted DSP+FPGA control platform that can be adapted from most existing centralized control systems (CCSs) of modular converters. In this article, the influence of synchronization accuracy (SA) on converter harmonics under carrier-based PWM is first investigated, followed by the study of communication latency's impact on the system control frequency. Subsequently, the synchronization method of a combined oversampling clock and data recovery (CDR) plus precision time protocol (PTP) method is presented. Furthermore, a communication protocol to maximize control frequencies and a system-level control strategy are elaborated. Finally, controller- and converter-level experimental results are demonstrated on a 520-V, 20-A, SiC-MOSFET-based IMU prototype at 120-kHz equivalent switching frequency, achieving a well-performed +/- 12.5-ns SA and 60-kHz control frequency.