Distributed MPPT Method for Smart Converter PV Systems
Electronic power processing technologies being developed now have the potential to revolutionize the way electricity is generated, distributed, and used. Over the past ten years, there has been increased incorporation of power electronics converters in "more electric" cars, ships, and airplanes to replace thermo-mechanical, mechanical, hydraulic, and pneumatic primary and secondary power systems. These converters have been introduced with the goals of reducing the size, weight, and maintenance and operational costs of these power systems, while increasing efficiency, safety, reliability, and optimizing mission-specific objectives. While energy efficiency is mostly being pursued through system-level power management and converter integration, power density increases are being addressed by the use of new materials, increased levels of integration, and innovative circuit designs. The recent increased availability of experimental active silicon carbide (SiC) and gallium nitride (GaN) devices has opened new opportunities for designing power converters that operate at increased switching frequencies with higher voltages and lower losses, which enables the reduction of the size and weight of the passive components for energy storage. However, switching devices introduce electromagnetic interference (EMI) problems into the system.
In order to avoid interference between different systems, the EMI noise emissions from the power converters need to be limited, and compliance with certain electro-magnetic compatibility (EMC) standards is regularly required. EMI filters are inevitably made part of power electronics systems to provide attenuation for EMI noise, but the additional EMI filter weight may diminish the benefits power electronic converters have over traditional systems, and even make the total weight and size greater. Therefore, it is a big challenge for modern power electronic system design to integrate the power converter and EMI filter together to minimize total weight/size and thus improve system power density.
Minimizing conducted EMI noise to meet the standards often involves trial and error. Despite this prevalent tactic, there have been systematic EMI mitigation techniques and design procedures developed over the years. This paper summarizes some of the authors' research efforts towards improvements in system EMI noise reduction and EMI filter weight/size optimization. The paper addresses several issues and approaches to system EMI modeling, EMI filter design, and weight/size optimization and integration together with examples of the EMI noise measurement results. EMI noise attenuation methods are discussed in detail, and key issues in filter design optimization process are presented and illustrated with the EMI filter test results. Possible improvements in power density through compact filter design and filter integration are also shown. The results are presented in the form of "nuggets" that highlight the basic ideas and their possible impact, but do not provide great detail on the technical contributions - these details can be found in the referenced papers.