Hardware-in-the-Loop Characterization of Source-Affected Output Characteristics of Cascaded H-Bridge Converter

Abstract

Recent trends in power system design such as an increasing share of renewable energy sources and integration of power electronics equipment for medium voltage applications are creating different subsystem interactions that require proper investigation, understanding, description, and estimation of global system stability through impedance-admittance measurements and identification. Four-quadrant Cascaded H-Bridge topology features high output voltage resolution and high effective switching frequency which enables high-dynamic, high-fidelity voltage perturbation injection for medium voltage impedance measurement. This paper assesses the impact that the active element on the input side has on the output side, where the injection of the perturbation signal is realized. Models of the input and output element are developed as well as the model of the connected system. To validate the theoretical developments, a new method to measure the single-phase output dynamics in the dq-frame is proposed and the measurement is performed using offline and real-time simulations on a hardware-in-the-loop platform.

Terminal characteristics measurements and analysis of the three‐phase Active Front‐End converter building block

“…Thus, it can be concluded that outside of this range, and in general, outside of the output voltage control range, the output impedance has little influence on the system. In conjunction with the results from [19], it can be concluded that the output impedance has little effect on the control-to-output characteristics of the CHB beyond 50 Hz. Nevertheless, the presented system does feature certain limitations such as the limited frequency range in which the measurement is performed.…”

“…The MV-CHB converter topology consisting of a step-down MV-MWT with 15 secondary phase-shifted outputs and 15 low-voltage cells is presented in Figure 1. The nominal parameters of this topology, such as current and voltage ratings, as well as the grid synchronisation and modulation strategies have already been presented in [15,19,20]. Each PEBB, presented in Figure 2, comprises an input filter, a three-phase AFE, a dc-link capacitor and a single-phase HB.…”

“…The key contributions of the work presented here are as follows: Hardware development of the three‐phase AFE and control platform implementation of the AFE based on a large‐scale industrial control platform. Implementation of a standalone system for input admittance and output impedance measurement of the AFE intended to support further CHB converter cell development. Experimental measurement of the output impedance required for source‐affected characterisation of the MV‐CHB PEBB [19]. …”

“…Experimental measurement of the output impedance required for source‐affected characterisation of the MV‐CHB PEBB [19].…”

“…On the other side, the AFE and the HB need to be decoupled and the AFE should not limit the output bandwidth of the HB stage. The element linking the two converters is the output impedance of the AFE [19].…”