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as higher flexibility and lower cost, it has been widely used in the communication of multi-area interconnected
power systems [3–5] .

An important indicator to measure power system operation quality is the fluctuation in frequency, and load
frequency control (LFC) is widely used to maintain frequency interchanges at scheduled values and stifle
frequency fluctuation caused by load disturbances [2,6,7] . Under the open communication infrastructure, the
sensor in each area collects data information. Then, data is transmitted to the decentralized controller under
the shared but band-limited network. The corresponding control commands are issued to actuators in each
area respectively. However, due to the introduction of the network, the design and operation of LFC face some
new challenges, such as node collision, data loss and network-induced delay [8–10] .

Due to different locations of sub-region power grids and the wide distribution of system components, multi-
channel transmission is inevitable in multi-area interconnected power systems, while most of the existing
results [10–13] take the general assumption that sampled data is packaged into a single packet to transmit, which
is not applied in large-scale multi-area interconnected power systems. On the other hand, the shared network
has limited bandwidth, where the simultaneous transmission under multiple channels may cause node con-
gestion. To solve this problem, scheduling protocols have been presented to decide which node to gain access
to the communication network [15? ] .

Generally, multi-channel scheduling includes Round-Robin (RR) scheduling [16,17] , try-once-discard (TOD)
scheduling [18,19] , and stochastic scheduling [20] . Under the RR scheduling protocol, each node is transmitted
periodically with a fixed period whose value is the total number of transmission channels. Under the TOD
scheduling, the sensor node with the largest scheduling error has access to the channel. Recently, a time-delay
analysis method has been discussed to derive stability criteria for networked control systems (NCSs) which
are scheduled by the above three communication protocols [14,21] . Besides, a hybrid system method has been
employed to analyze NCSs with variable delays under the TOD communication protocol [19] , where a partial
exponential stabilization criterion has been derived. The ∞ filtering of NCSs with multiple nodes has been
investigated [22] , in which TOD protocol is used to schedule sampled data.

This paper studies the ∞ LFC for multi-area interconnected power systems with decentralized controllers
under the shared but band-limited network. RR and TOD protocols are used to schedule the sampling in-
formation of different sub-grids, which could greatly improve communication efficiency. Through linear ma-
trix inequality (LMI) technology and Lyapunov analysis methods, sufficient conditions that guarantee the
prescribed ∞ performance of the studied system are derived. Decentralized controller gains and protocol
parameters are obtained simultaneously. The main contributions are summarized as follows.

(1) RR and TOD protocols are used to deal with the multi-node collision of large-scale power systems, which
improve communication efficiency greatly. Compared with the existing LFC methods [10,23,24] , the scheduling
process under multi-area transmission schemes is investigated.

(2) An networked power system impulsive closed-loop model is well constructed, which covers the multi-
channel scheduling, packet dropout, disturbance, and network-induced delays in a unified framework. Com-
pared with the system without disturbance [19] , this paper studies the anti-disturbance performance of the
studied system. An ∞ LFC method is presented to obtain decentralized controller gains and scheduling
protocol parameters simultaneously.

1.1. Notations
Throughoutthispaper, R standsforthen-dimensionalEuclideanspacewithvectornorm k · k. {· · · } and
{· · · } denote the block-diagonal matrix and block-column vector, respectively. The superscript stands for