The dc in a power system may be caused by geomagnetic disturbances that are the result of solar storms and high-altitude nuclear detonations. Increased inverter-based generation is also contributing to small dc injection into the power systems. The resultant dc could have serious consequences for the power systems as it may drive power transformers into saturation, cause transformer internal heating, cause large draw of reactive power, and misoperation of protective relays. This letter proposes a novel power electronics-based dc mitigation approach that involves a transformerless series active filter integrated between the neutral point and ground of power transformers serving multiple purposes. The first objective is to surpass the effect of dc injection, the second goal is voltage regulation, and the third is to provide harmonic isolation or impedance balancing. The proposed device is currently being developed on a 7.2-kV/240-V single-phase transformer; however, the solution is also relevant for 24–500-kV networks. The system circuitry, operation, and control are implemented and verified for this letter in a controller hardware-in-the-loop (C-HIL) test setup using a Typhoon HIL-402 simulator. Results indicate that our approach is a promising alternative to traditional neutral capacitor-blocking strategies.

中文翻译：

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基于变流器的电力系统保护输配电网络中的直流电流

电力系统中的直流电可能是由太阳风暴和高空核爆炸引起的地磁扰动引起的。增加基于逆变器的发电量也有助于向电力系统注入少量直流电。由此产生的直流会对电力系统产生严重后果，因为它可能会导致电力变压器进入饱和状态，导致变压器内部发热，导致大量无功功率消耗和保护继电器误动作。这封信提出了一种基于电力电子的新型直流抑制方法，该方法涉及在电力变压器的中性点和接地之间集成一个无变压器串联有源滤波器，用于多种用途。第一个目标是超越直流注入的效果，第二个目标是电压调节，三是提供谐波隔离或阻抗平衡。建议的设备目前正在 7.2-kV/240-V 单相变压器上开发；然而，该解决方案也适用于 24-500 kV 网络。系统电路、操作和控制在控制器硬件在环 (C-HIL) 测试设置中使用台风 HIL-402 模拟器实现和验证。结果表明，我们的方法是传统中性电容器阻断策略的有前途的替代方案。使用台风 HIL-402 模拟器在控制器硬件在环 (C-HIL) 测试设置中实现和验证此字母。结果表明，我们的方法是传统中性电容器阻断策略的有前途的替代方案。使用台风 HIL-402 模拟器在控制器硬件在环 (C-HIL) 测试设置中实现和验证此字母。结果表明，我们的方法是传统中性电容器阻断策略的有前途的替代方案。