Three-state switching cell (3SSC)-based non-isolated dc-dc boost-type converter with balanced output voltage and wide voltage conversion range

This work presents a non-isolated step-up dc-dc converter with wide voltage conversion range based on the three-state switching cell, which is suitable for distinct applications, e.g. renewable energy and uninterruptible power supply (UPS) systems. Prominent advantages can be addressed to the topology, i.e. continuous input current, thus making it a proper choice for the use of battery banks as the input voltage source; the ability to operate at high power, high-current levels while maintaining current sharing through the main switches without the need of special control schemes; reduction of size, weight, and volume of filter elements, which are designed for twice the switching frequency; the maximum voltage across the controlled switches is half of the total output voltage; naturally balanced voltages across the dc-link capacitors exist; and the voltages across the switches are naturally clamped to that across the output filter capacitor, avoiding the need for external snubbers. The complete qualitative analysis of the converter is presented, including the operating principle and a step-by-step design procedure. A transformerless online UPS topology is also briefly described as a potential application for the introduced converter. Finally, experimental waveforms obtained from a 1.55-kW prototype are shown and relevant issues are discussed.