Collaborative Research: Advanced and Highly Integrated Power Conversion Systems for Grid Stability and Resiliency

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To accelerate residential and commercial photovoltaic penetration to meet future utility and grid needs, energy storage and innovative power electronics need to be integrated into photovoltaic systems. The integration of energy storage into the photovoltaic system can enable grid support, load shifting, peak shaving, energy backup, reduced power loss in transmission and distribution networks, as well as optimization of power utilization. Transforming the grid into a more distributed configuration will require system capabilities well beyond today's simple grid-tied photovoltaic inverters. The goal of this project is to create scalable, modular, highly efficient, and flexible architecture and control for photovoltaic systems, energy storage, and the grid. This smart, highly integrated system will enable higher penetration of solar energy into the grid and disrupt the conventional energy system by delivering an integrated, efficient, and reliable solar energy solution. The higher penetration will lead to higher photovoltaic deployment and growth in photovoltaic industry, increase job creation, and boost economy. One fully integrated product will not only reduce installation cost and complexity but will also ensure simplified supply chain management from module supplier to end user. Such technological integration of hardware and advanced control systems with its modularity and expandability will pave way for even higher photovoltaic penetration. Educational outreach activities will be performed by integrating the proposed research to undergraduate or graduate level courses, making the hardware inverter testbed accessible to undergraduate and K-12 students, organizing panels and tutorials at IEEE power electronics and power and energy society conferences, and hosting open-access webinars. Engaging minority and under-represented groups will be implemented throughout such outreach activities.The project team will propose the development and deployment of a novel design of a highly efficient, modulator, distributedly controlled, and scalable power system with the capability for integration and coordination of photovoltaic, local energy storage, and a bidirectional smart micro-inverter. The hardware consists of a three-port single-stage power conversion circuit integrated with photovoltaic, battery, and grid with a novel topology known as the flying capacitor multilevel inverter with Gallium Nitride devices. The proposed decentralized model predictive control will address challenges including state-of-charge control of energy storage, photovoltaic smoothing, maximum power point tracking, and energy arbitrage. This will support grid functionalities, provide energy shifting/peak shaving, and apply power management strategy for stable and predictable power in both grid-connected and islanded modes. Moreover, a novel optimization problem for coordinating multiple three-port inverters considering optimal trade-off between voltage regulation and reactive power sharing and technical constraints on voltage and reactive power is to be formulated. A primal-dual gradient based distributed solving algorithm is to be developed to address the unique challenges including non-separable objective function, unavailable global average voltage, and globally coupled reactive power constraints. The proposed algorithm will not only effectively and efficiently solve the formulated microgrid control problem but will also benefit the distributed optimization and control community by providing a useful method for distributedly solving a general form optimization problem.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.