INVESTIGATION OF DISTRIBUTED CONTROLS AND COMMUNICATIONS IN CASCADED MULTI-LEVEL INVERTER
1 online resource (139 pages) : PDF
University of North Carolina at Charlotte
This thesis investigates a cascaded H-bridge multi-level inverter topology (CHB-MLI). It utilizes a unique methodology that converts the conventional DC voltage output of a solar photo-voltaic (PV) panel to generate switched quasi-square wave AC voltages. When aggregated, the CHB-MLI realizes a superior quality multi-level waveform. This alternative approach offers advantages, such as, extracting maximum power at panel level and realizing system-level cost benefits. Sorted Stair Case Modulation is the control technique implemented on CHB-MLI. This control scheme is evaluated against two different sorting cycle scenarios: half-cycle and quarter-cycle. The simulation model is run for these scenarios (on developed case studies) with variety of solar irradiance, coefficient of variation and mean irradiance levels, when CHB-MLI is integrated with the load. The resultant percentage yields and the voltage and current ripple at panel level are documented for each scenario. It is noted that increasing the sorting frequency improves the yield and reduces the ripple when irradiance conditions are uniform; however, under non-uniform irradiance conditions, negligible improvement is observed. The benefits of distributed controller over a single master controller are analyzed. Also, the required parameters for the execution of distributed controls are identified. Multiple communication protocols are reviewed, keeping the focus on simple implementation and reducing wire requirements. Three protocols ---Universal Asynchronous Receiver Transmitter (UART), Serial Peripheral Interface (SPI), and Inter-Integrated Circuit (I2C)--- are studied considering various attributes. I2C protocol is implemented on the developed laboratory prototype of seven-level CHB-MLI, integrated with resistive load.
Zhao, TiefuCecchi, Valentina
Thesis (M.S.)--University of North Carolina at Charlotte, 2018.
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