The technology of virtual synchronous machine (VSM) is attracting interest of researchers as it controls converters mimicking the synchronous machine’s response so as to provide inertial support for power electronics dominated smart grids. For the VSM-based microgrid, its slow dynamics are dominated by synchronous generators (SGs) and the VSM control loops, which makes it possible to model this microgrid into an equivalent SG (EqSG) model. This paper proposes a robust secondary frequency control design method for the VSM-based low voltage (LV) microgrid cluster (MGC) using equivalent modeling. The EqSG model is used to construct the MGC model so as to reduce the model order and the complexity of controller synthesis. Modeling errors caused by the EqSG model and different operating conditions are integrated into the MGC model as unstructured uncertainties. The proposed secondary frequency control strategy is based on the distributed-centralized hybrid control structure to coordinate frequency restoration among LV microgrids. Structured $\mu $ -synthesis is applied for tuning control parameters realizing $H_{\infty }$ robust performance against unstructured uncertainties. To reduce the communication resource consumption, an event-triggered mechanism considering communication delay is introduced in the robust secondary frequency control strategy. The triggering condition is analyzed using a Lyapunov function to guarantee $H_{\infty }$ robust stability. Simulation and real-time experiment results on a MGC composed of four CIGRÉ benchmark LV microgrids are presented to demonstrate the effectiveness of the proposed control strategy.

中文翻译：

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使用等效建模的基于虚拟同步机的微电网集群的鲁棒二次频率控制

虚拟同步电机 (VSM) 技术吸引了研究人员的兴趣，因为它控制转换器模仿同步电机的响应，从而为电力电子主导的智能电网提供惯性支持。对于基于 VSM 的微电网，其缓慢的动态由同步发电机 (SG) 和 VSM 控制回路主导，这使得可以将该微电网建模为等效的 SG (EqSG) 模型。本文使用等效建模为基于 VSM 的低压 (LV) 微电网集群 (MGC) 提出了一种稳健的二次频率控制设计方法。EqSG模型用于构建MGC模型，以降低模型阶数和控制器综合的复杂度。由 EqSG 模型和不同操作条件引起的建模误差作为非结构化不确定性整合到 MGC 模型中。所提出的二次频率控制策略基于分布式集中混合控制结构来协调低压微电网之间的频率恢复。结构化的 $\亩 $ -综合用于调整控制参数实现 $H_{\infty }$ 对非结构化不确定性的稳健表现。为了减少通信资源消耗，鲁棒次频控制策略中引入了考虑通信延迟的事件触发机制。使用李雅普诺夫函数分析触发条件以保证 $H_{\infty }$ 稳健的稳定性。展示了由四个 CIGRÉ 基准低压微电网组成的 MGC 的仿真和实时实验结果，以证明所提出的控制策略的有效性。