Module integrated converters (MIC), also called micro inverter, in single phase have witnessed recent market success due to unique features (1) improved energy harvest, (2) improved system efficiency, (3) lower installation costs, (4) plug-N-play operation, (5) and enhanced flexibility and modularity. The MIC sector has grown from a niche market to mainstream, especially in the United States. Due to the fact that two-stage architecture is commonly used for single phase MIC application. A DC-DC stage with maximum power point tracking to boost the output voltage of the Photovoltaic (PV) panel is employed in the first stage, DC-AC stage is used for use to connect the grid or the residential application. As well known, the cost of MIC is key issue compared to convention PV system, such as the architecture: string inverter or central inverter. A high efficiency and density DC-DC converter is proposed and dedicated for MIC application. Assuming further expansion of the MIC market, this dissertation presents the micro-inverter concept incorporated in large size PV installations such as MW-class solar farms where a three phase AC connection is employed. A high efficiency three phase MIC with two-stage ZVS operation for grid tied photovoltaic system is proposed which will reduce cost per watt, improve reliability, and increase scalability of MW-class solar farms through the development of new solar farm system architectures. This dissertation presents modeling and triple-loop control for a high efficiency three-phase four-wire inverter for use in grid-connected two-stage micro inverter applications. An average signal model based on a synchronous rotation frame for a three-phase four-wire inverter has been developed. The inner current loop consists of a variable frequency bidirectional current mode (VFBCM) controller which regulates output filter inductor current thereby achieving ZVS, improved system response, and reduced grid current THD. Active damping of the LCL output filter using filter inductor current feedback is discussed along with small signal modeling of the proposed control method. Since the DC-link capacitor plays a critical role in two-stage micro inverter applications, a DC-link controller is implemented outside of the two current control loops to keep the bus voltage constant. In the end, simulation and experimental results from a 400 watt prototype are presented to verify the validity of the theoretical analysis.

Renewable energy source plays an important role in the energy cogeneration and distribution. Traditional solar-based inverter system is two stages in cascaded, which has a simpler controller but low efficiency. A new solar-based single-stage grid-connected inverter system can achieve higher efficiency by reducing the power semiconductor switching loss and output stable and synchronized sinusoid current into the utility grid. Controlled by the digital signal processor, the inverter can also draw maximum power from the solar array, thereby maximizing the utilization of the solar array. In Chapter 1, a comparison between the traditional two-stage inverter and the single-stage inverter is made. To increase the ability of power processing and enhance the efficiency further, a full-bridge topology is chosen, which applies the phase-shift technique to achieve zero-voltage transition. In Chapter 2, average-mode and switch-mode Pspice simulations are applied. All the features of the inverter system are verified, such as stability, zero voltage transition and feed-forward compensation, etc. All these simulation results provide useful design tips for prototyping. In Chapter 3, a phase-shift controller is designed based on UCC3895. Also, a detailed design procedure is given, including key components selection, transformer and inductor design and driver circuits design. In Chapter 4, experimental results of a prototype DC/DC converter are presented and analyzed. By optimization of the circuit, the problems of the prototype are solved and the prototype is working stably. The thesis' conclusion is given in Chapter 5.

To relieve energy shortage and environmental pollution issues, renewable energy, especially PV energy has developed rapidly in the last decade. The micro-inverter systems, with advantages in dedicated PV power harvest, flexible system size, simple installation, and enhanced safety characteristics are the future development trend of the PV power generation systems. The double-stage structure which can realize high efficiency with nice regulated sinusoidal waveforms is the mainstream for the micro-inverter. This thesis studied a double stage micro-inverter system. Considering the intermittent nature of PV power, a PFC was analyzed to provide additional electrical power to the system. When the solar power is less than the load required, PFC can drag power from the utility grid. In the double stage micro-inverter, the DC/DC stage was realized by a LLC converter, which could realize soft switching automatically under frequency modulation. However it has a complicated relationship between voltage gain and load. Thus conventional variable step P&O MPPT techniques for PWM converter were no longer suitable for the LLC converter. To solve this problem, a novel MPPT was proposed to track MPP efficiently. Simulation and experimental results verified the effectiveness of the proposed MPPT. The DC/AC stage of the micro-inverter was realized by a BCM inverter. With duty cycle and frequency modulation, ZVS was achieved through controlling the inductor current bi-directional in every switching cycle. This technique required no additional resonant components and could be employed for low power applications on conventional full-bridge and half-bridge inverter topologies. Three different current mode control schemes were derived from the basic theory of the proposed technique. They were referred to as Boundary Current Mode (BCM), Variable Hysteresis Current Mode (VHCM), and Constant Hysteresis Current Mode (CHCM) individually in this paper with their advantages and disadvantages analyzed in detail. Simulation and experimental iv results demonstrated the feasibilities of the proposed soft-switching technique with the digital control schemes. The PFC converter was applied by a single stage Biflyback topology, which combined the advantages of single stage PFC and flyback topology together, with further advantages in low intermediate bus voltage and current stresses. A digital controller without current sampling requirement was proposed based on the specific topology. To reduce the voltage spike caused by the leakage inductor, a novel snubber cell combining soft switching technique with snubber technique together was proposed. Simulation and experimental waveforms illustrated the same as characteristics as the theoretical analysis. In summary, the dissertation analyzed each power stage of photovoltaic micro-inverter system from efficiency and effectiveness optimization perspectives. Moreover their advantages were compared carefully with existed topologies and control techniques. Simulation and experiment results were provided to support the theoretical analysis.

In the field of renewable energy, solar photovoltaic is growing exponentially. Grid-tied PV micro-inverters have become the trend for future PV system development because of their remarkable advantages such as enhanced energy production due to MPPT implementation for each PV panel, high reliability due to redundant and distributed system architecture, and simple design, installation, and management due to its plug-and-play feature. Conventional approaches for the PV micro-inverters are mainly in the form of single-phase grid connected and they aim at the residential and commercial rooftop applications. It would be advantageous to extend the micro-inverter concept to large size PV installations such as MW-class solar farms where threephase AC connections are used. The relatively high cost of the three-phase micro-inverter is the biggest barrier to its large scale deployment. Increasing the switching frequency may be the best way to reduce cost by shrinking the size of reactive components and heat-sink. However, this approach could cause conversion efficiency to drop dramatically without employing soft switching techniques or using costly new devices. This dissertation presents a new zero voltage switching control method that is suitable for low power applications such as three-phase micro-inverters. The proposed hybrid boundary conduction mode (BCM) current control method increases the efficiency and power density of the micro-inverters and features both reduced number of components and easy digital implementation. Zero voltage switching is achieved by controlling the inductor current bidirectional in every switching cycle and results in lower switching losses, higher operating frequency, and reduced size and cost of passive components, especially magnetic cores. Some iv practical aspects of hybrid control implementation such as dead-time insertion can degrade the performance of the micro-inverter. A dead-time compensation method that improves the performance of hybrid BCM current control by decreasing the output current THD and reducing the zero crossing distortion is presented. Different BCM ZVS current control modulation schemes are compared based on power losses breakdown, switching frequency range, and current quality. Compared to continuous conduction mode (CCM) current control, BCM ZVS control decreases MOSFET switching losses and filter inductor conduction losses but increases MOSFET conduction losses and inductor core losses. Based on the loss analysis, a dual-mode current modulation method combining ZVS and zero current switching (ZCS) schemes is proposed to improve the efficiency of the micro-inverter. Finally, a method of maintaining high power conversion efficiency across the entire load range of the three-phase micro-inverter is proposed. The proposed control method substantially increases the conversion efficiency at light loads by minimizing switching losses of semiconductor devices as well as core losses of magnetic components. This is accomplished by entering a phase skipping operating mode wherein two phases of an inverter are disabled and three inverters are combined to form a new three-phase system with minimal grid imbalance. A 400W prototype of a three-phase micro-inverter and its hybrid control system have been designed and tested under different conditions to verify the effectiveness of the proposed controller, current modulation scheme, and light load efficiency enhancement method.

Nanoscale p-channel transistors under negative gate bias at an elevated temperature show threshold voltage degradation after a short period of stress time. In addition, nanoscale (45 nm) n-channel transistors using high-k (HfO2) dielectrics to reduce gate leakage power for advanced microprocessors exhibit fast transient charge trapping effect leading to threshold voltage instability and mobility reduction. A simulation methodology to quantify the circuit level degradation subjected to negative bias temperature instability (NBTI) and fast transient charge trapping effect has been developed in this thesis work. Different current mirror and two-stage operation amplifier structures are studied to evaluate the impact of NBTI on CMOS analog circuit performances for nanoscale applications. Fundamental digital circuit such as an eleven-stage ring oscillator has also been evaluated to examine the fast transient charge transient effect of HfO2 high-k transistors on the propagation delay of ring oscillator performance. The preliminary results show that the negative bias temperature instability reduces the bandwidth of CMOS operating amplifiers, but increases the amplifier's voltage gain at mid-frequency range. The transient charge trapping effect increases the propagation delay of ring oscillator. The evaluation methodology developed in this thesis could be extended to study other CMOS device and circuit reliability issues subjected to electrical and temperature stresses.

This thesis introduces the design and analysis of a single-stage inverter. A circuit was designed and simulated as a proof of concept to investigate the possibility of using boost and buck-boost converters to provide an AC output. The proposed circuit utilizes non-synchronous boost and buck-boost converters due to their simplicity in control signals as opposed to synchronous converters. The application of the proposed inverter is for use with individual solar cells. The aim of the inverter for a single cell is to improve the efficiency of a solar panel, whose performance is limited to the performance of the least efficient cell. With each cell independent of any other cell in the solar panel, the overall efficiency of the panel can be improved. This circuit uses a 3.6VDC input from the solar cell to produce a 10VPP 60Hz square wave output. The inverter consists of a solar cell, two DC-DC converters, two linear dropout (LDO) regulators, a square wave generator, and a switching circuit . The design and analysis of all parts were investigated individually in detail. The different parts of the circuit were then simulated using LTspice before testing the overall circuit. Simulation results demonstrate the feasibility of the proposed inverter with all design requirements but efficiency meeting or exceeding the goals.

As the world strives towards finding alternative sources of power generation, photovoltaic generation has become an increasingly prevalent alternative energy source on power systems world-wide. This paper studies the effects that incorporating photovoltaic generation has on the existing power systems and their power system protection schemes. Along with the addition of this emerging alternative energy source comes the volatility of PV power generation as cloud-cover produces erratic variations in solar irradiance and PV power production. Such variations in PV power may lead to unfavorable operating conditions and power system failures. The issues addressed in this paper include a study of inverter harmonic levels for variations in DC voltage and power, and a study of power system protection failures caused by cloud-induced PV power variations. Such issues are addressed so as to provide a better understanding of the effects that cloud-induced PV power generation variability has on power systems and its protection schemes.

The automotive sector finds itself undergoing a significant and substantial transformation, propelled by the pronounced proliferation of electric vehicles (EVs) and autonomous driving technologies. As the industry proactively adapts to embrace this, an increasingly pressing demand becomes evident for higher performance, reliability, sustainability, and speed. Semiconductor packages emerge as primary catalysts within this ongoing revolution, positioned squarely at the forefront to assume a critical and indispensable function in facilitating the realization of these fundamental objectives. Commercial vehicle manufacturers are taking steps to respond to these demands for sustainability and speed, the driving force in facilitating this being the shift from Si IGBTs to SiC MOSFETs. Silicon Carbide is an increasingly popular choice in inverter module fabrication for electric vehicle applications owing to its inherent characteristics such as reduced on resistance, higher blocking voltage, and higher temperature stability that enable high power density, increased efficiency, and speeds. This work focuses on developing and fabricating a high-density 1.7 kV, 300 A SiC MOSFET half-bridge power module tailored for a 280-320 kW, 2-level inverter configuration. Co-designed with the busbar and gate driver, the custom power module stresses efficient heat dissipation, minimized parasitic inductance, and a compact footprint. Key target parameters to achieve optimal performance include a Rdson below 20 mΩ, Rthjc under 0.2 K/W and a switching time below 20 ns. The proposed module features a double-sided cooling sandwiched structure, an integrated thermistor for health and degradation monitoring, and incorporates three Wolfspeed 3rd generation 1.7 kV, 18 mΩ devices per switch position. The simulated power loop inductance is 14.5 nH, the simulated parasitic resistance is 0.265 m, and the simulated junction-to-case thermal resistance is 0.12182 ℃/W. To keep the die temperature below 150 ℃, a cooling coefficient of 5500 W/m2 is necessary. / Master of Science / The automotive sector is in the midst of a major transformation, propelled by the noticeable spread of electric vehicles (EVs) and autonomous driving technologies. As the industry actively evolves to accommodate this, an increasingly pressing demand becomes apparent for higher performance, reliability, sustainability, and speed. Semiconductor packages are at the forefront of this transformation, playing a crucial role in achieving these goals. Commercial vehicle makers are taking steps to respond to these demands for sustainability and speed, the driving force for this being the shift from Si IGBTs to SiC MOSFETs. Silicon Carbide is an increasingly popular choice in inverter module fabrication for electric vehicle applications owing to its inherent characteristics such as reduced resistance, higher blocking voltage, and higher temperature stability that enable high power density, increased efficiency, and speeds. This study focuses on creating a compact and efficient power module for commercial electric vehicle applications. The designed module is capable of handling high power levels while remaining compact, thus prioritizing power density. This is carefully designed to ensure it cools down effectively, minimizes unnecessary energy losses, and has a small footprint. Certain key features, such as its commutation speed, current carrying capacity, and thermal and mechanical limitations, were also studied. A temperature sensor was incorporated to monitor its health and performance over time. Simulations were performed to validate that this module performs well in terms of its resistances in the electrical conduction path and the oath of heat dissipation.

A market review on Hybrid Inverters with Back-Up (HIBU) is presented, selecting products from eleven global inverter manufacturers. A systemic review of all the productsis performed, along with a general comparison of their main features. Trends in power ranges, battery voltages, back-up connection scheme and switching times are then highlighted and other more peculiar characteristics are assessed. A focus on potential applications in the Swedish market is put, considering an average Swedish household consumption profile. Ten from the available software for modeling photovoltaics applications are then reviewed finding PVsyst, Homer and SAM the most suitable tools for computing systems with HIBU. Finally, a case study is simulated on PVsyst showing the influence of the battery size on the percentage of covered load for different values of grid availability. The influence of different locations and different battery discharging strategies is also assessed, critically evaluating the reliability of the model used on PVsyst and stating the main shortcomings.

Electric and more-electric vehicle proliferation continues unabated as government mandates worldwide demand fuel economies in excess of what conventional internal combustion engines are capable of. Vehicle electrification, to any degree, is perceived to be the means by which automotive companies may meet these targets. Electrification introduces a myriad of problems including cost, weight and reliability, all of which must be addressed in their own right. The rapid commercialisation of wide-bandgap semiconductor materials which, as a whole, exhibit properties superior to ubiquitous Silicon, provides the opportunity for power electronic converter minimisation and efficiency maximisation, easing the challenge of meeting current and incoming standards. This thesis concerns itself with the design methodology of a highly power dense converter, as applied to a three-phase inverter. By using figures of merit, simple modelling techniques and novel discrete component selection tools, a converter is designed that is capable of switching 30kW of electric power at 100kHz in a small package. Testing results show that the converter, with a simple forced air heatsinking solution, can effectively switch 9kW of power and is capable of reaching 15kW. Given the temperature rise of one phase leg of the inverter relative to the others, a superior heatsink design would allow the inverter to reach its rated power levels. / Dissertation / Master of Applied Science (MASc)