Thesis

Grid-connected solid oxide fuel cell using NI back to back inverter board and labview-multisim

The objective of this project is to develop a hardware-in-loop grid-connected Solid Oxide Fuel cell (SOFC) as a distributed generator using Labview-Multisim co-simulation and National Instrument (NI) inverter board. The model consists of a fuel cell (FC), dc-ac inverter and power electronic parameters to interconnect with loads and grid. First, the fuel cell model developed in Labview along with controller model and co-simulated with the inverter model in Multisim. Then the simulated model compared with the hardware implemented model using the same inverting concept with the same driver, filter and load. The comparison between simulation output and hardware- in loop result is monitored in the Labview for accuracy and case studies. FC-based power generation systems are expected to become a clean and reliable sources of future distributed generation (DG) applications. Two types of fuel cells -proton exchange membrane fuel cells (PEMFCs) and solid-oxide fuel cells (SOFCs) - are perfect candidates for DG applications. In this project SOFC is used as a high efficiency dc source. The SOFC model implemented in Labview based on defined assumptions and criteria and it consists of an electrochemical and a thermodynamic submodels. The responses are studied under constant and variant fuel flow rate of operation and steady state temperature mode. This model has a good potential to be used in any real-time applications. The NI compactRIO DC/AC inverter board consists of two, three-phase two-level Insulated Gate Bipolar Transistor (IGBT) inverters, two single phase rectifier bridges, reconfigurable controller, and appropriate interconnections between components. The board can incorporate both analog and digital inputs with appropriate interfaces. The analog plant circuitry of the NI board's inverter implemented in Multisim. The controller, a Field-Programmable Gate Array (FPGA), is modeled in LabVIEW based on a three stage flowchart of closed loop continuous time (i.e. rise time, steady state error and maximum overshoot), floating point (discretized) and fixed point digital controller implementation. The power electronic circuits in Multisim and mathematical models of fuel cell and FPGA controller in labVIEW co-simulated in labVIEW providing a potential for validating, analyzing and troubleshooting large power plants by running real-time computer simulations. This new approach development tool saves so much time and cost at a high accuracy and efficiency. Once the design is done, the SOFC source can be replaced easily by any other distributed generators like photovoltaic panel and the power system can be used in other applications such as vehicular applications.

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