Impact on Renewable Energy Sources on Harmonic Levels in the Future UK Power Grid: Modelling, Assessment and Mitigating Solutions

英国承诺到2050年将温室气体排放量在1990年的基础上至少减少80%。要实现这一目标，就需要在能源的使用和产生方式上作出重大改变（例如，通过加热和运输电气化）。为了减少我们对化石燃料的依赖，需要将大量可再生能源（RESs）整合到电网中。可再生能源包括不依赖化石燃料和核能的能源，如太阳能、风能、潮汐能和波浪能。一些可再生能源已经被成功地纳入（例如，抽水蓄能），它们通常不被归类为“RESs”，因为这个术语指的是通过电源转换器连接到电网的设备。虽然可再生能源的好处是无可争议的，应该促进其安装，但大量这些装置的集成需要发展新的范例和方法，以维持可靠和安全的电力系统。RESs具有与传统能源不同的某些特性：它们比传统能源更不可控，它们会导致意想不到的功率流模式，它们会影响电压和电流波形以及电力的整体功率质量。本提案将重点研究由于RESs在英国电网中的谐波传播。谐波是频率倍于基频的电流和电压分量，它们是由电源变流器的工作产生的。虽然低谐波水平是可以容忍的，不会影响电网运行，但谐波水平的增加会产生不利影响，包括：损耗增加、效率降低、误操作和设备寿命缩短，以及有害保护跳闸。由于谐波的长期影响，其成本不容易确定，但电网运营商和用户已经认识到，谐波水平的提高不利于电网的有效运行。更重要的是，它们可能会损害未来RESs的集成。本提案旨在评估RESs对未来电网的谐波影响。进行这种评估需要开发RESs和电力系统的准确模型。同时，由于所涉及的组件的数量，这些模型需要某种形式的简化。以前的研究要么集中在详细的电力变换器模型上，要么集中在使用简化变换器表示的大型电力系统模型上。该NIA旨在将这两个方面结合在一个模型中，该模型能够正确地表示RESs产生的谐波，电压水平之间的谐波传递，以及系统中谐波水平的统计变化，用于不同程度的RESs渗透。这项研究将涉及与两个工业伙伴——国家电网和可测量有限公司，以及德克萨斯大学奥斯汀分校的密切合作。这项研究的影响将是广泛的：所开发的模型将有助于学术界理解研究大型能源系统谐波行为的最佳方法。这项工作将协助系统操作员评估新的RESs对电力系统的影响。此外，这项研究将为电力质量标准和谐波缓解解决方案的未来发展提供信息。该项目的最终目标是最大限度地减少未来电网中谐波问题的发生，不仅在英国，而且在全球范围内，允许平稳和清洁地整合越来越多的RESs。此外，它将有利于英国作为一个整体，在保持这种无处不在的基础设施的运营和效率方面，同时帮助政府实现减少二氧化碳排放的目标。

The UK is committed to reducing its greenhouse gas emissions by at least 80% by 2050, relative to 1990 levels. Meeting this target will require a significant shift in the way energy is used (for example, through electrification of heat and transport) and generated. To reduce our dependency on fossil fuels, significant levels of Renewable Energy Sources (RESs) will need to be integrated into the power grid. RESs include energy sources that do not rely on fossil fuels and nuclear energy, such as solar, wind, tidal and wave. Some sources of renewable energy have been successfully incorporated (for example, pumped-hydro), and they are generally not classified as 'RESs' as this term refers to devices that are connected to the grid by means of power converters. While the benefits of RESs are undisputable and their installation should be facilitated, the integration of large amounts of these devices requires the development of new paradigms and methods to maintain a reliable and safe power system. RESs have certain characteristics that differentiate them from traditional sources: they are less controllable than traditional energy sources, they cause unintended power flow patterns, and they impact voltage and current waveforms and the overall power quality of electricity. This proposal will focus on the study of harmonic propagation in the UK power grid due to RESs. Harmonics are current and voltage components at frequencies multiple of the fundamental, and they are generated by the operation of the power converters. While low harmonic levels are tolerated and do not impact grid operation, increasing harmonic levels have detrimental effects including: increased losses, reduced efficiency, misoperation and reduced lifetime of equipment, and nuisance protection tripping. While the costs of harmonics are not easy to determine because of their long-term effect, it has become accepted by the power grid operators and users that increasing harmonic levels are detrimental for efficient grid operation. More importantly, they may compromise the future integration of RESs. This proposal aims at assessing the harmonic impact of RESs in the future power grid. Carrying out this assessment requires the development of accurate models of both RESs and of the power system. At the same time, these models requires some form of simplification because of the number of components involved. Previous research has focused on either detailed power converter models, or the use of a large power system model with simplified converter representation. This NIA aims at combining both aspects in a model which is able to represent correctly harmonic generation from RESs, the transfer of harmonics between voltage levels, and the representation of statistical variations of harmonic levels in the system, for varying levels of penetration of RESs. This research will involve close collaboration with two industrial partners, National Grid and Measurable Ltd, and with the University of Texas at Austin. The impact of this research will be widespread: the models developed will help the academic community in understanding the best approaches to study harmonic behaviour of large energy systems. This work will assist the system operator in assessing the impact of new RESs on the power system. Furthermore, this research will inform the future developments of power quality standards and of harmonic mitigating solutions. The ultimate goal of this project is to minimise the occurrence of harmonic problems in the future power grid, allowing for a smooth and clean integration of increasing amounts of RESs, not only in the UK, but on a global scale. Furthermore, it will benefit the UK as a whole in terms of maintaining the operations and efficiency of this ubiquitous infrastructure, whilst helping the government to meet targets for reducing CO2 emissions.