human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "a survey on modeling of microgrids from fundamental physics to phasors and voltage sources"
  Abstract: Microgrids have been identified as key components of modern electrical systems to facilitate the integration of renewable distributed generation units. Their analysis and controller design requires the development of advanced (typically model-based) techniques naturally posing an interesting challenge to the control community. Although there are widely accepted reduced order models to describe the dynamic behavior of microgrids, they are typically presented without details about the reduction procedure---hampering the understanding of the physical phenomena behind them. Preceded by an introduction to basic notions and definitions in power systems, the present survey reviews key characteristics and main components of a microgrid. We introduce the reader to the basic functionality of DC/AC inverters, as well as to standard operating modes and control schemes of inverter-interfaced power sources in microgrid applications. Based on this exposition and starting from fundamental physics, we present detailed dynamical models of the main microgrid components. Furthermore, we clearly state the underlying assumptions which lead to the standard reduced model with inverters represented by controllable voltage sources, as well as static network and load representations, hence, providing a complete modular model derivation of a three-phase inverter-based microgrid.

Connected through hyperedge HE-1 (induced by source paper "estimation of photovoltaic generation forecasting models using limited information"):
  with members:
    - "model estimation for solar generation forecasting using cloud cover data"
    - "innovative second generation wavelets construction with recurrent neural networks for solar radiation forecasting"

Connected through hyperedge HE-2 (induced by source paper "an energy based analysis of reduced order models of networked synchronous machines"):
  with members:
    - "an internal model approach to optimal frequency regulation in power grids with time varying voltages"

Connected through hyperedge HE-3 (induced by source paper "a scalable line independent design algorithm for voltage and frequency control in ac islanded microgrids"):
  with members:
    - "voltage stabilization in dc microgrids an approach based on line independent plug and play controllers"
    - "plug and play voltage and frequency control of islanded microgrids with meshed topology"

Connected through hyperedge HE-4 (induced by source paper "a tool for stability and power sharing analysis of a generalized class of droop controllers for high voltage direct current transmission systems"):
  with members:
    - "modeling and control of hvdc transmission systems from theory to practice and back"

Connected through hyperedge HE-5 (induced by source paper "kron reduction methods for plug and play control of ac islanded microgrids with arbitrary topology"):
  with members:
    - "plug and play voltage and frequency control of islanded microgrids with meshed topology"
    - "kron reduction of generalized electrical networks"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.SY(Systems and Control)