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: "distributed robust adaptive frequency regulation of power grid with renewable integration"
  Abstract: This paper investigates distributed angular frequency regulation of multi-machine power systems with wind generations when wind power signals' frequencies are known (and unknown). The challenge is to regulate angular frequencies under fast changing and unpredictable wind generations. To address the issue, we split unknown signals into three parts according to their frequency ranges and design an (adaptive) internal model to reconstruct the low and medium frequency parts. We integrate heterogeneous grid components to deal with fast changing signals. At each bus with wind power generations, a battery energy storage system is used to filter out high frequency components of wind generations. At generator bus, demand response is utilized to deal with their medium frequency components and a synchronous generator is exploited to handle their low frequency components. At load bus, demand response handles low and medium frequency components. The proposed controllers ensure exponential stability (and asymptotic convergence) of system states with respect to their desired signals. Simulations on the IEEE 68-bus test system are conducted to demonstrate the effectiveness of the proposed controllers.

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)