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: "multi level power imbalance allocation control for secondary frequency control in power systems"
  Abstract: This paper focuses on secondary frequency control of large-scale power systems. First a centralized and a consensus control based distributed control law are presented, then a multi-level control law, named Multi-Level Power-Imbalance Allocation Control (MLPIAC), for the large-scale power systems partitioned into more than one region. The centralized and distributed control law are applied within each region and over the regions respectively. Besides restoring nominal frequency with a minimized control cost, MLPIAC also considers the transient behavior of the system after a disturbance. We present a control strategy different from the one applied in the Power-Imbalance Allocation Control (PIAC), which also enhances the transient behavior of the frequency through an accelerated convergence of the control inputs eliminating overshoots in MLPIAC. In the level of the distributed control over the regions, the consensus of the marginal costs can be accelerated through a single parameter. Furthermore, because the number of regions is smaller than that of nodes, MLPIAC is more effective to obtain the minimized cost than the purely distributed control law. The asymptotic stability of MLPIAC is proven using the Lyapunov method and the performance is evaluated through simulations.

Connected through hyperedge HE-1 (induced by source paper "passivity based design of sliding modes for optimal load frequency control"):
  with members:
    - "a novel reduced model for electrical networks with constant power loads"
    - "an internal model approach to optimal frequency regulation in power grids with time varying voltages"

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)