Architecture for Grid-connected Inverters with Power Semiconductor Filters
DescriptionAs environmental awareness increases, there is growth in the penetration of distributed generation (DG) systems located at the point of utilization for a single structure or a part of a microgrid operating in parallel with, or independently from, the main power grid. For example, Hong Kong officially launched the feed-in tariff policy scheme for photovoltaic systems and renewable energy certificates in 2018. Compared to traditional centralized power systems, DG systems have many potential advantages - providing clean power, reducing carbon emissions, improving efficiency, optimizing asset utilization, and improving system safety, stability, capacity, flexibility and reliability.Typical DG systems firstly convert electric energy generated by micro-sources into a DC form at a regulated voltage. Then, the DC power is converted into an AC form for the power grid by a grid-connected inverter. The power conversion stage of the grid-connected inverter consists of a switching network and an output filter. As advances in microelectronics and packaging technology continue to miniaturize the switching network, the volume of the output filter becomes a key factor limiting the power density of the inverter.In general, the output filter has its volume reduced as its order increases. However, high-order filters contain a plurality of reactive elements and thus exhibit a plurality of resonant frequencies. Circuit resonances among the reactive elements may then arise. In the past decade, a great deal of research has been done to solve this resonance phenomenon and improve the system performance, but the technologies developed still face some common challenges in dealing with unknown, non-negligible grid impedances and non-linear loads on system stability under different grid conditions. In addition, thermal management, acoustic noise, and electromagnetic coupling between components within limited space present challenges to circuit designers.The project aims to investigate a new perspective of replacing the output filter with a power semiconductor filter (PSF) to control the inverter output current. In addition to eliminating filter resonance, the physical size of the filter section can also be reduced. The PSF technique was first used to control the input current of switching converters. Hence, apart from leading to a more comprehensive and accurate understanding of the use of PSF in different types of converters, this project will also help to achieve the long-term goal of miniaturizing the volume of the filter section and advancing the performance characteristics of this new kind of inverter for DG systems consisting of multi-parallel connected inverters.
|Effective start/end date
|1/01/20 → 27/12/23