A Selective Polarity DC-DC Converter with Virtually Infinite Voltage Levels

Indiana University-Purdue University Indianapolis (IUPUI)This research introduces a new design of a converter modified from SEPIC converter (Single end primary inductive converter), capable of generating desired voltage levels and polarities. The new switching converter topology allows for boost and buck of the input voltage theoretically achieving infinite positive and negative voltage levels. The proposed topology utilizes single high frequency switch to perform the power conversion which simplifies the design of the gate driver, but meanwhile, it still retains the ability to provide a wide range of output voltage. Mathematical modeling of the converter and computer simulations are validated by experimental data. To verify its performance a prototype was designed and built. It is experimentally proven that the circuit can generate a desired voltage in the range of voltages up to ±170 V, delivering 480 Watts of power to a resistive load

Solar Micro Inverter

Indiana University-Purdue University Indianapolis (IUPUI)The existing topologies of solar micro inverter use a number of stages before the DC input voltage can be converted to AC output voltage. These stages may contain one or more power converters. It may also contain a diode rectifier, transformer and filter. The number of active and passive components is very high. In this thesis, the design of a new solar micro inverter is proposed. This new micro inverter consists of a new single switch inverter which is obtained by modifying the already existing single ended primary inductor (SEPIC) DC-DC converter. This new inverter is capable of generating pure sinusoidal waveform from DC input voltage. The design and operation of the new inverter are studied in detail. This new inverter works with a controller to produce any kind of output waveform. The inverter is found to have four different modes of operation. The new inverter is modeled using state space averaging. The system is a fourth order system which is non-linear due to the inherent switching involved in the circuit. The system is linearized around an operating point to study the system as a linear system. The control to output transfer function of the inverter is found to be non-minimum phase. The transfer functions are studied using root locus. From the control perspective, the presence of right half zero makes the design of the controller structure complicated. The PV cell is modeled using the cell equations in MATLAB. A maximum power point tracking (MPPT) technique is implemented to make sure the output power of the PV cell is always maximum which allows full utilization of the power from the PV cell. The perturb and observe (P&O) algorithm is the simplest and is used here. The use of this new inverter eliminates the various stages involved in the conventional solar micro inverter. Simulation and experimental results carried out on the setup validate the proposed structure of inverter