Hybrid double flying capacitor multicell converter and its application in grid-tied renewable energy resources

Multicell multilevel voltage source power converters are the state-of-the-art and key elements for harnessing and integration of medium-voltage high-power renewable energy resources. This study proposes a novel hybrid topology for double flying capacitor multicell (DFCM) converters that is suitable for grid-tied renewable energy systems. The proposed power converter is realised by cascade connection of one DFCM converter and one full-bridge converter (FBC) comprising a floating-capacitor. The floating-capacitor voltage of the FBC is regulated naturally at its requisite voltage level because of the existence of the abundant redundant charging/discharging states provided by the proposed switching and modulation pattern for the suggested hybrid converter. Hence the proposed control technique not only preserves the natural balancing for the FC voltages of the DFCM converter but also provides natural balancing for the floating-capacitor voltage of the FBC. The main objective of the FBC is to generate additional intermediate voltage steps to double the number of DFCM converter´s voltage levels for enhancing power quality significantly. The proposed hybrid DFCM converter is simulated to inject/absorb active/reactive-power provided and harvested from renewable energy resources into/from electric power grid. Furthermore, experimental measurements of the proposed hybrid power converter are also presented to validate its viability, merits, effectiveness and the proposed modulation and control strategy.