| This study is the comparison of the design and analysis of the Stacked Multicell Converter (SMC) with the Neutral Point Clamped (NPC) converter. Multilevel converters are becoming increasingly popular for high power applications, because they can considerably reduce the output voltage and current harmonics by using several voltage levels while still switching the devices at the same frequency. The diode clamped converter (DCC) and the SMC converter are two types of multilevel converters which both use one DC bus subdivided into a number of voltage levels by a series string of capacitors. This kind of structure can reduce the blocking voltage requirement of each switching device. The three-level DCC converter, which is also called the NPC converter, has been put into practical use for large capacity ac motor drives in industry. Due to the voltage limitations of the switching devices, series connection of the devices is required in high-voltage and high-power applications with the NPC structure. Higher level DCC can solve this problem, but another problem of voltage unbalance between the outer do capacitors and inner do capacitors occurs. Although methods have been proposed to balance the capacitor voltage, they have not been put into practice by the industry.; In this thesis we present a new topology called the SMC which allows increasing input voltage level, while not increasing the switching device stresses by the use of floating capacitors. This thesis gives the design of the SMC including a method of pre-charging the floating capacitors, selection of the floating capacitors, and analysis of the commutation requirements. Both the converters are simulated using EMTDC and PWM techniques and compared in theory and experiment. |
