Comprehensive Analysis of DC Link Capacitors Used in Cascaded H-Bridge Motor Driver

Abstract

An essential part of inverter design is selecting direct current-Link Capacitors (DCLC) for Medium-Voltage Cascaded H-bridge motor Drivers (MV-CHBMD). This article analyzes capacitor configuration for MV-CHBMD to improve the quality of driver output and input current depending on an analysis of DCLC current effects. The techniques were employed with two-level converters to find the harmonics, and the root mean square (RMS) value of the capacitor current has been expanded to seven-level MV-CHBMD. Additionally, a novel mathematical technique has been recommended for determining the RMS current and voltage ripple of the DCLC. The proposed MATLAB simulation technique provides a comprehensive analysis of the outcome results. This allows for easy customization to other modulation methods and application to higher-level MV-CHBMD. Specifically, it calculates the worst-case scenario for the DC-link voltage in a 1000-horsepower and 3.3-kV system. The study also presents empirical evidence that specific system components endure excessive stress. This information is valuable for accurately specifying system components and ensuring optimal system design in the MV-CHBMD system. This article examines the potential impact of standard mode voltage on the bearings of medium-voltage motors. In addition, an optimal approach for selecting DCLCs in a multilevel cascaded H-bridge (CHB) motor driver strategy is proposed, effectively eliminating voltage stress on switching devices. The effectiveness of these systems is demonstrated by presenting simulation results. A comprehensive study analyzed the performance of various inverter levels, including total harmonic distortion (THD) and efficiency. The DC link was constructed using the MATLAB platform to conduct a thorough analysis. The proposed approach exhibits superior performance and lower costs compared to traditional methods. The experimental work and test confirm the simulation results. The test result showed that selecting DCLCs in a CHB provides a higher-quality output waveform into CHB, which supports the controlling structure and reduces the probability of malfunctions.