Derived from classic DC-AC multilevel converters, hybrid multilevel converters can combine distinct advantages, thus receiving increasing attention for their widespread industrial applications recently. The Active Neutral Point Clamped (ANPC) converter offers redundant switching states to achieve a better control and more even loss distribution compared to Neutral Point Clamped (NPC) converter. However, in terms of five-level converters, currently the only topology applied in industrial application is the Flying-Capacitor based Neutral Point Clamped converter (FCANPC), which gives a relatively good performance with a simple structure. Despite its advantages, the uneven loss distribution cannot be disregarded as a substantial drawback to affect the power processing capability. The Dual Flying Capacitor Neutral Point Clamped (DFCANPC) converter has been newly proposed to provide better loss balancing and "soft commutation" to have a higher power capability and efficiency.

In this thesis, traditional multilevel topologies such as Cascaded H-Bridge converter, Diode Clamped converter, and Flying Capacitor converter are summarized, followed by popular modulation schemes including carrier-based modulation, Space Vector Modulation and Selective Harmonic Elimination modulation. Thermal models and cooling strategies are then briefly discussed. As the main focus, thermal analysis and comparison regarding the five-level FCANPC converter and the newly proposed DFCANPC converter is reported in this thesis. A PSIM model has been built for verification of loss balancing performance of the DFCANPC converter.

This thesis applies a fixed ON-time switching technique to a resonant switched-capacitor converter, called the 3X RTBSC-A converter, which is studied for maximum power point tracking (MPPT) applications. The previous converter, the 3X RTBSC converter, was unable to achieve full-range voltage gain regulation for relatively light loads. However, with a new switching technique known as Switching Technique A, full-range voltage gain regulation for all loads is completely possible. In addition, the converter achieves zero-voltage switching (ZVS) to retain a high efficiency. A mathematical analysis of the ideal circuit was completed to show the conducting states, voltage gain derivation, and component stresses. Under this analysis, the prototype circuit was designed with a maximum power level of 162 W and a resonant frequency of 100 kHz. Simulations in the LTspice software proved that the circuit would not be able to achieve full-range voltage gain regulation with regular 50% duty cycle switching. In addition, details are provided in the design of the prototype's control circuit and driver circuit used to create and execute Switching Technique A. An open loop experiment demonstrates that the voltage gain of the prototype circuit closely resembles the waveforms calculated from the ideal gain formula. Also, a relatively high efficiency is recorded for each load tested with a maximum recorded efficiency of 0.9544. In addition, examination of the steady state waveforms prove that the prototype circuit is executing ZVS. To prepare the prototype for the MPPT experiment, a sensing circuit is designed to feed data to the microcontroller. A simple perturb and observe (P&O) algorithm is programmed to find the maximum power point (MPP). The specifications of the solar panel are also presented. The results of the MPPT experiment demonstrate that the MPP found by the MPPT algorithm closely follows the actual MPP that was found manually. In addition, the prototype achieved efficiencies between 0.87 and 0.92 during the MPPT experiment. The 3X RTBSC-A converter still has the potential to achieve higher efficiencies as indicated by the report on the original circuit.

This thesis presents a new dual resonant switched-capacitor converter topology that inverts the polarity of input voltages and can regulate the gain continuously between 0 and –1, even at light load operation. A literature review on the development and improvement of switched-capacitor converters over the years is presented in Chapter 1. The switched capacitor in the presented converter is charged and discharged through resonant inductors, eliminating large current spikes and charge sharing losses associated with pure switched-capacitor converters. This resonance allows for ZCS turn-on of all switches and ZCS turn-off of all diodes. Chapter 2 presents a detailed analysis of the dual resonant switched-capacitor polarity inverter, in which a voltage gain curve in four distinct operating modes is provided, along with a detailed discussion of boundary conditions between modes. Voltage and current stresses of all components are analyzed, and design guidelines for designing the presented converter from a specified input voltage, output voltage, and output power are presented. In addition, a regenerative snubber to eliminate undesirable parasitic ringing is provided. An 80V to –35V ~ –72V open loop prototype with peak efficiency 97.0% and maximum power 120W was built to verify the operation of the converter, and the experimental results from this prototype are presented in Chapter 3. Finally, in Chapter 4, several extensions of the topology are presented to reduce the step-down ratio of the converter or to apply the topology to step-up applications.

The electrical power grid is the biggest man-made system, and one of the most complex ones. This system has been up and evolving from about a century into the large connected system we have today. However, innovations are very few in recent years, and it becomes more outdated as days go by. Moreover, we need to modify the operational status quo - not environmentally friendly because of its predominant coal-based generation. Investigation of the grid’s behavior and study of control techniques under new scenarios, such as renewable energy generation, is needed to update the grid to cope with new challenges brought by implementation of modern technologies enhancing our power systems.

In this thesis, effects of Reactive Power will be discussed, VAR compensation techniques such as static, switched capacitor banks and static VAR compensators are simulated on a grid with high solar energy penetration. Two different software are used to simulated a 12.47 kV, 7 MW circuit, and VAR compensation is studied in conjunction with load curves. The VAR Compensation methods are effectively employed, and discussions made regarding their effects.

A new technique of optimal capacitor placement and sizing for losses reduction is developed, using power flow optimization and graphical tools to achieve the most efficient and effective place and size for banks placement. Using easy-to-implement steps, it enables losses and costs reduction , increasing grid’s efficiency. The validity of the approach is tested in the same grid previously studied, confirming its functioning and effectively reducing over 5% of circuit losses.