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Item A Bipolar SEPIC Converter with Wide Output Voltage Range(Office of the Vice Chancellor for Research, 2015-04-17) Liu, Kaiyang; Izadian, AfshinEnergy Systems and Power Electronics Laboratory, Purdue School of Engineering, IUPUI. In order to pursue a perfect inverter, a new inverter technology is designed based on SEPIC converter that can efficiently generate pure sinusoidal waveforms and operate in a wide range of loading conditions. The groundbreaking design of the new inverter is that, for the first time, the number of high-frequency switching-transistors is reduced to one. By changing the switching frequency and duty cycle for the switch, the voltage-level of the output signal will be continuously controlled to produce a nearly pure sinusoidal waveform, and the voltage-level can reach infinity without using any switch map in theory. In order to achieve the DC to AC conversion, inversing the polarity and the boost operation for the output voltage are the two main problems in the process of achieving this goal. To proof the possibility of the new inverter technology, a research for a bipolar SEPIC converter is firstly proposed in order to achieve the voltage polarity inversion and the boost operation. The research basically use a diode to regulate the current direction that goes through the load. By changing the direction of the diode, the polarity of the output voltage can be inversed. For the boost operation, a simulation setup in Simulink and some actual tests have been used to find out the sizes for each elements in the circuit that can boost the output voltage of the converter to 110V at a specific frequency and duty cycle of the only switch. The result of the research had showed that this converter not only had the capability to provide a very wide output voltage ranges and power levels, but also can generate output voltage and power levels for positive and negative polarities.Item SEPIC DC – AC Converter Design and Operation(Office of the Vice Chancellor for Research, 2013-04-05) Hegde, Shweta; Izadian, AfshinThis paper focuses on the design and study of operation of the SEPIC converter which is modified to function as an inverter i.e. converts DC input to AC output. The modified converter consists of reduced number of switches which increases the efficiency and also improves the quality of the waveforms generated. The conventional SEPIC converter consists of two inductors, two capacitors, one transistor switching at high frequency and a diode. The modified SEPIC replaces the diode with a polarity reversing switch component. This component contains two reverse connected transistors T1 and T2 which are synchronized with the polarity of the output waveform. This new inverter is capable of producing pure sinusoidal waveform with only three switches of which only one is switched at high frequency, Q. The new inverter is found to operate in four different modes of operation to produce positive and negative cycles of output voltage. The modes 1 and 2 of operation have the switches Q and T1 operating and produce positive peak and the modes 3 and 4 of operation have the switches Q and T2 operating and produce negative peak. The inductor connected in the input side of the inverter is chosen to be large enough to maintain continuous conduction. State Space Averaging technique is used to model the system where the currents through the inductors and voltages across the capacitors are considered to be the state variables. The state space representation of each mode of operation is obtained and the system is averaged over the positive peak and negative peak separately. The state space model of the inverter is validated using MATLAB/SIMULINK. The inverter model was simulated using SimPowerSystems tool box of MATLAB and found to produce pure sinusoidal waveform. The harmonics were found to be reduced to a great extent.