Operation of microgrid at constant frequency with a standby backup grid-forming generator
Operation of microgrid at constant frequency with a standby backup grid-forming generator
复制标题
带备用并网发电机的微电网恒频运行
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
Daming Zhang
中科院分区：
文献类型：
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作者：
Daming Zhang
并网发电机在孤岛微电网的运行中至关重要。如果没有适当的补救措施，它的故障可能会导致整个微电网系统的崩溃。本文提出了在主并网发电机的基础上，增加备用并网发电机的方案。在无故障条件下，主并网发电机只输出系统所需的真实的功率，并将系统所需的无功功率传输到其伴随的无功功率补偿器，而备用并网发电机作为电网支持发电机工作，输出少量的真实的功率和接近零的无功功率，从而实现解耦PQ控制。研究了两个案例。在第一种情况下，主备用电网形成发电机与硬连线通信链路并排工作，而在第二种情况下，两个远程定位并且没有通信链路。当主并网发电机发生故障并被迫与电网断开时，备用并网发电机接管并网角色，整个系统可以继续平稳运行。相比之下，在第一种情况下控制超越的转换几乎是无缝的，而在第二种情况下存在检测时间延迟，该检测时间延迟可以通过将电压变化检测与频率漂移检测相结合来缩短。与传统的频率下垂控制相比，系统工作在恒定频率，降低了运算复杂度。
Grid-forming generator is of paramount importance in the operation of an islanded microgrid. A fault in it without proper remedy could lead to collapse of the whole microgrid system. In this paper, besides a main grid-forming generator, a standby backup grid-forming generator is adopted in the system to prevent this from happening. Under no fault condition, the main grid-forming generator takes de-coupled PQ control by outputting only real power demanded by the system and transferring system-demanded reactive power to and from its accompanying reactive power compensator while the standby grid-forming generator works as a grid-supporting generator and outputs a small amount of real power and nearly zero reactive power. Two cases have been studied. In the first case the main and standby backup grid-forming generators work side by side with hardwired communication link while in the second case, two are remotely located and has no communication link. When a fault occurs to the main grid-forming generator and forces its disconnection from the grid, the backup grid-forming generator takes over the grid-forming role and the whole system can continue to operate smoothly. Comparatively transitions of control overtake in the first case is almost seamless while in the second case there is a detection time delay which could be shortened by combining voltage variation detection with frequency drift detection. Compared with conventional frequency droop control, the system operates at constant frequency to reduce operation complexity.