Hard macrocells for DC/DC converter in automotive embedded mechatronic systems

A novel configurable DC/DC converter architecture, to be integrated as hard macrocell in automotive embedded systems, is proposed in the paper. It aims at realizing an intelligent voltage regulator. With respect to the state of the art, the challenge is the integration into an automotive-qualified chip of several advanced features like dithering of switching frequency, nested control loops with both current and voltage feedback, asynchronous hysteretic control for low power mode, slope control of the power FET gate driver, and diagnostic block against out-of-range current or voltage or temperature conditions. Moreover, the converter macrocell can be connected to the in-vehicle digital network, exchanging with the main vehicle control unit status/diagnostic flags and commands. The proposed design can be configured to work both in step-up and step-down modes, to face a very wide operating input voltage range from 2.5 to 60 V and absolute range from −0.3 to 70 V. The main target is regulating all voltages required in the emerging hybrid/electric vehicles where, besides the conventional 12 V DC bus, also a 48 V DC bus is present. The proposed design supports also digital configurability of the output regulated voltage, through a programmable divider, and of the coefficients of the proportional-integrative controller inside the nested control loops. Fabricated in 0.35 μm CMOS technology, experimental measurements prove that the IC can operate in harsh automotive environments since it meets stringent requirements in terms of electrostatic discharge (ESD) protection, operating temperature range, out-of-range current, or voltage condition

A Viable Residential DC Microgrid for Low Income Communities – Architecture, Protection and Education

The availability of fossil fuels in the future and the environmental effects such as the carbon footprint of the existing methodologies to produce electricity is an increasing area of concern. In rural areas of under-developed parts of the world, the problem is lack of access to electrification. DC microgrids have become a proven solution to electrification in these areas with demonstrated exceptional quality of power, high reliability, efficiency, and simplified integration between renewable energy sources (principally solar PV) and energy storage. In the United States, a different problem occurs that can be addressed with the same DC microgrid approach that is finding success internationally. In disinvested, underserved communities with high unemployment and low wages, households contribute a significant portion of their income towards the fixed cost of their electrical utility connection, which by law must be supplied to every household. In order to realize such a microgrid in these communities, there are three major areas which need to be accounted for. Firstly, there needs to be a custom architecture for the community under consideration and it needs to be economical to match the needs of the underserved community. Secondly, DC microgrid for home energy interconnection is potentially less complex and less expensive to deploy, operate and maintain however, faster protection is a key element to ensuring resilience, viability and adoptability. Lastly, these types of efforts will be sustainable only if the people in the community are educated and invested in the same as they are the key stakeholders in these systems. This dissertation presents an approach to make the DC Microgrid economically feasible for low income households by reducing the cost they incur on electric bills. The approach is to overlay a DC system into homes that have a utility feed in order to incorporate renewable energy usage into an urban setting for the express purpose of driving down individual household utility costs. The results show that the incorporation of a certain level of “smart” appliances and fixtures into the renovation of vacated homes and the use of a microgrid to enable sharing of renewable energy, such as solar power combined with energy storage, between homes in the proposed architecture yields the least expensive option for the patrons. The development of solid state circuit breakers that interface between the microgrid and the home DC power panels helps in faster protection of the DC system. In this dissertation, a SiC JFET based device is designed and built to protect against DC faults at a faster rate than the available solutions. The prototype is tested for verification and used to discriminate against short circuit faults and the results show the successful fault discrimination capabilities of the device. A basic system level simulation with the protection device is implemented using Real Time Hardware in the loop platform. Finally, as a part of engaging the community members, the high school kids in the area who might potentially be living in some of the houses in this community are being educated about the microgrid, appliances and other technologies to get a better understanding of STEM and hopefully inspiring them to pursue a career in STEM in the future

A Viable Residential DC Microgrid for Low Income Communities – Architecture, Protection and Education

The availability of fossil fuels in the future and the environmental effects such as the carbon footprint of the existing methodologies to produce electricity is an increasing area of concern. In rural areas of under-developed parts of the world, the problem is lack of access to electrification. DC microgrids have become a proven solution to electrification in these areas with demonstrated exceptional quality of power, high reliability, efficiency, and simplified integration between renewable energy sources (principally solar PV) and energy storage. In the United States, a different problem occurs that can be addressed with the same DC microgrid approach that is finding success internationally. In disinvested, underserved communities with high unemployment and low wages, households contribute a significant portion of their income towards the fixed cost of their electrical utility connection, which by law must be supplied to every household. In order to realize such a microgrid in these communities, there are three major areas which need to be accounted for. Firstly, there needs to be a custom architecture for the community under consideration and it needs to be economical to match the needs of the underserved community. Secondly, DC microgrid for home energy interconnection is potentially less complex and less expensive to deploy, operate and maintain however, faster protection is a key element to ensuring resilience, viability and adoptability. Lastly, these types of efforts will be sustainable only if the people in the community are educated and invested in the same as they are the key stakeholders in these systems. This dissertation presents an approach to make the DC Microgrid economically feasible for low income households by reducing the cost they incur on electric bills. The approach is to overlay a DC system into homes that have a utility feed in order to incorporate renewable energy usage into an urban setting for the express purpose of driving down individual household utility costs. The results show that the incorporation of a certain level of “smart” appliances and fixtures into the renovation of vacated homes and the use of a microgrid to enable sharing of renewable energy, such as solar power combined with energy storage, between homes in the proposed architecture yields the least expensive option for the patrons. The development of solid state circuit breakers that interface between the microgrid and the home DC power panels helps in faster protection of the DC system. In this dissertation, a SiC JFET based device is designed and built to protect against DC faults at a faster rate than the available solutions. The prototype is tested for verification and used to discriminate against short circuit faults and the results show the successful fault discrimination capabilities of the device. A basic system level simulation with the protection device is implemented using Real Time Hardware in the loop platform. Finally, as a part of engaging the community members, the high school kids in the area who might potentially be living in some of the houses in this community are being educated about the microgrid, appliances and other technologies to get a better understanding of STEM and hopefully inspiring them to pursue a career in STEM in the future

Efficiency Optimization in Digitally Controlled Flyback DC-DC Converters Over Wide Ranges of Operating Conditions

Because of increasingly demanding energy programs and initiatives, it is required to maintain high efficiency in various DC-DC converter applications over wide ranges of operating conditions. To achieve these efficiency goals, this thesis introduces an efficiency optimization approach, which can be applied to given power stages. In the proposed optimization approach, power stage design parameters and controller parameters are concurrently optimized over a range of operating conditions based on power loss models and multi-variable non-linear constrained optimization. A digital controller facilitates on-line efficiency optimization by storing the optimum controller parameters in a look-up table. A flyback DC-DC converter, commonly used in low output power applications, is adopted for experimental verifications of the proposed optimization approach. A valley switching technique is employed to significantly decrease MOSFET turn-on switching loss in discontinuous conduction mode (DCM), and solutions to a problem related to undesirable frequency hopping, commonly observed in other valley switching schemes, are proposed and discussed. A gain-scheduled compensator and a new control scheme, named k-control, are implemented for consistent transient responses over different operating conditions. Finally, simplified sensing and analog-to-digital (A/D) conversion techniques are proposed, targeting a low-cost, small-size and low-pin-count (≤ 8) digital controller IC chip implementation