Indiana University-Purdue University Indianapolis (IUPUI) / This thesis proposes two new topologies for Uninterrupted Power Supply (UPS), and a grid-tie microinverter. The first topic will discuss an on-line transformerless UPS system based on the integrated power electronics converters that is able to control the input power factor, charge the battery, and guarantee backup operation of the system. The main advantages of the proposed UPS are active power factor correction (PFC) without the need of a complex control scheme, and integrated functions of the battery charger circuit and PFC with only three power switches. Operation modes of the system and the PWM strategy is presented in detail. The second topic discussed is of a proposed circuitry for a single-phase back-to-back converter for UPS applications. The main advantages of this topology is higher number of levels at the rectifier side, less number of power switches, and no need for a boost inductor at the input side of the converter. The last topic discussed is of a proposed patent pending microinverter. This topic was a project funded by the National Science Foundation, and its aim was to help commercialize the research. This project proposes a solution for a solar inverter called Delta Microinverter that allows easier and faster installation as well as power conversion with higher efficiency. Delta Microinverters innovation is found in its patent-pending shape and in its patent-pending circuitry, i.e., electronics mounted inside of the Delta Microinverter. The Delta Microinverters shape has a housing configured for rapid mounting using a single fastener and its power electronics configuration offers an optimized relationship between the number of levels and number of power switches.