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: "design and stability of load side primary frequency control in power systems"
  Abstract: We present a systematic method to design ubiquitous continuous fast-acting distributed load control for primary frequency regulation in power networks, by formulating an optimal load control (OLC) problem where the objective is to minimize the aggregate cost of tracking an operating point subject to power balance over the network. We prove that the swing dynamics and the branch power flows, coupled with frequency-based load control, serve as a distributed primal-dual algorithm to solve OLC. We establish the global asymptotic stability of a multimachine network under such type of load-side primary frequency control. These results imply that the local frequency deviations on each bus convey exactly the right information about the global power imbalance for the loads to make individual decisions that turn out to be globally optimal. Simulations confirm that the proposed algorithm can rebalance power and resynchronize bus frequencies after a disturbance with significantly improved transient performance.

Connected through hyperedge HE-1 (induced by source paper "performance and resilience of cyber physical control systems with reactive attack mitigation"):
  with members:
    - "optimal attack against cyber physical control systems with reactive attack mitigation"
    - "data injection attacks on smart grids with multiple adversaries a game theoretic perspective"
    - "bad data injection attack and defense in electricity market using game theory study"
    - "playing atari with deep reinforcement learning"

Connected through hyperedge HE-2 (induced by source paper "global analysis of synchronization performance for power systems bridging the theory practice gap"):
  with members:
    - "graph laplacian spectrum and primary frequency regulation"
    - "performance measures in electric power networks under line contingencies"
    - "engineering inertial and primary frequency response for distributed energy resources"
    - "performance tradeoffs of dynamically controlled grid connected inverters in low inertia power systems"

Connected through hyperedge HE-3 (induced by source paper "exponential stability of primal dual gradient dynamics with non strong convexity"):
  with members:
    - "stochastic variance reduction methods for policy evaluation"
    - "stochastic variance reduction methods for saddle point problems"
    - "convergence analysis of saddle point problems in time varying wireless systems control theoretical approach"

Connected through hyperedge HE-4 (induced by source paper "less is more real time failure localization in power systems"):
  with members:
    - "failure localization in power systems via tree partitions"
    - "power grid vulnerability to geographically correlated failures analysis and control implications"

Connected through hyperedge HE-5 (induced by source paper "robust control for renewable integrated power networks considering input bound constraints and worst case uncertainty measure"):
  with members:
    - "a framework for robust assessment of power grid stability and resiliency"
    - "decentralized robust control for damping inter area oscillations in power systems"
    - "game theoretic multi agent control and network cost allocation under communication constraints"
    - "robust stability assessment in the presence of load dynamics uncertainty"

Connected through hyperedge HE-6 (induced by source paper "frequency violations from random disturbances an mcmc approach"):
  with members:
    - "engineering inertial and primary frequency response for distributed energy resources"
    - "line failure probability bounds for power grids"

Connected through hyperedge HE-7 (induced by source paper "graph laplacian spectrum and primary frequency regulation"):
  with members:
    - "performance measures in electric power networks under line contingencies"

Connected through hyperedge HE-8 (induced by source paper "a framework for robust assessment of power grid stability and resiliency"):
  with members:
    - "lyapunov functions family approach to transient stability assessment"
    - "efficient synchronization stability metrics for fault clearing"
    - "geometry based estimation of stability region for a class of structure preserving power grids"

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)