Three-phase Cascaded H-bridge Inverter Research Articles

Fault Diagosis of CHB Inverter Using Machine Learning

Renewable energy has gained popularity due to depleting natural resources and escalating fossil fuel and nuclear pollution. Power electronic engineers design grid-connected power conversion systems. MLIs provide more power and solutions. Cascaded H-Bridge (CHB) MLIs start with two or more 3L single-phase H-bridge inverters. Each H-bridge may produce three separate voltage levels. Combining the separated dc voltage sources produces a stepped output voltage with a step size equal to the magnitude of the connected sources. The present work develops a method for detecting and resolving switch failures in a three-phase CHB inverter, ensuring system dependability and allowing for system redundancy. The recommended approach uses Wavelet transform to extract features, then Decision Tree classifier to detect and characterise defects. Increased classification accuracy shows the DT-based fault diagnosis system's efficiency in identifying inverter switch faults.

Research on Power Equalization of Three-Phase Cascaded H-Bridge Photovoltaic Inverter Based on the Combination of Hybrid Modulation Strategy and Zero-Sequence Injection Methods

Due to the nonuniform solar irradiance, unequal ambient temperatures, or inconsistent degradation of photovoltaic (PV) modules in three-phase cascaded H-bridge (CHB) PV inverter, the unbalanced output power among PV modules will lead to the imbalanced power between phases and bridges, resulting in unbalanced or even distorted grid current between three phases, which cannot meet the requirements of grid codes. Concerning this issue, this article proposes a novel power equalization method based on the combination of hybrid modulation strategy and zero-sequence injection methods, which deals with interbridge power imbalance by hybrid modulation and interphase power imbalance by zero-sequence injection methods. By utilizing the proposed method, three-phase-balanced grid currents with low total harmonic distortion are able to be achieved even when the interbridge and the interphase power are seriously unbalanced. In addition, each H-bridge cell in three-phase CHB inverter uses square-wave modulation, which maximizes the dc-side voltage utilization of each H-bridge cell, thus extending its power balance region. Experimental results achieved by a laboratory prototype of a three-phase seven-level CHB inverter demonstrate both feasibility and validity of the proposed method.