Comparison of zero-sequence injection methods in cascaded H-bridge multilevel converters for large-scale photovoltaic integration

• Published in: IET renewable power generation 2017-04, Vol.11 (5), p.603-613
• Main Authors: Yu, Yifan, Konstantinou, Georgios, Townsend, Christopher D, Agelidis, Vassilios G
• Format: Article
• Language: English
• Subjects: bridge circuits; cascaded H‐bridge multilevel converter; large‐scale photovoltaic integration; large‐scale solar PV power plant; multilevel CHB converter; optimal zero‐sequence voltage injection method; power 10 kW; power convertors; power grids; PV power generation; Research Article; solar power stations; three‐phase balanced grid current; three‐phase seven‐level CHB converter prototype; unbalanced power generation; voltage 430 V
• ISSN: 1752-1416; 1752-1424; 1752-1424
• DOI: 10.1049/iet-rpg.2016.0621

Photovoltaic (PV) power generation levels in the three phases of a multilevel cascaded H-bridge (CHB) converter can be significantly unbalanced, owing to different irradiance levels and ambient temperatures over a large-scale solar PV power plant. Injection of a zero-sequence voltage is required to maintain three-phase balanced grid currents with unbalanced power generation. This study theoretically compares power balance capabilities of various zero-sequence injection methods based on two metrics which can be easily generalised for all CHB applications to PV systems. Experimental results based on a 430 V, 10 kW, three-phase, seven-level cascaded H-bridge converter prototype confirm superior performance of the optimal zero-sequence injection technique.