通过主动干扰抑制功能实现具有通信延迟的电力系统的分散负载频率控制
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IET Generation, Transmission & Distribution
Research Article
Decentralised load frequency control for
power systems with communication delays
via active disturbance rejection
ISSN 1751-8687
Received on 13th June 2017
Revised 18th October 2017
Accepted on 3rd November 2017
E-First on 12th February 2018
doi: 10.1049/iet-gtd.2017.0852
www.ietdl.org
Caifen Fu
1
, Wen Tan
1
1
School of Control & Computer Engineering, North China Electric Power University, Zhuxinzhuang, Dewai, Beijing, People's Republic of China
E-mail: fcf@ncepu.edu.cn
Abstract: A decentralised load frequency control (LFC) for multi-area power systems with communication delays is studied.
Active disturbance rejection control (ADRC) method is adopted to handle the communication delays. First the conventional
ADRC is tuned via the bandwidth method and it is shown that the achievable performance for delayed systems is no better than
proportional-integral-derivative (PID) controllers. Then a modified ADRC structure is discussed and it is shown that the
achievable performance is limited by the controller bandwidth. In order to improve the performance, a method to tune the
parameters of ADRC is proposed via the internal model control method. Simulation results show that the proposed method is
easy to apply and can achieve good damping performance.
1 Introduction
The problem of controlling the real power output of generating
units in response to changes in system frequency and tie-line power
interchange within specified limits is known as load frequency
control (LFC) [1]. It plays a major role in power system operation
and control.
In traditional LFC framework, the control signals are
transmitted through dedicated communication channels. In the past,
the delays in the transmission are neglected in traditional power
system since it is quite small compared with the dynamics of the
LFC systems [2, 3]. With the deregulation of the power generation
sector, an effective power system market needs an open
communication infrastructure to support the increasing
decentralised property of control processes. Therefore, in the near
future, the communication delay will become one of significant
uncertainties in the LFC synthesis/analysis due to expanding
physical setups, functionality, and complexity of a power system
[4–6]. In such a case, time delays cannot be ignored and may
degrade the dynamic performance or even lead to system instability
[7, 8].
At present, there is a rapid momentum in the advancement of
research in LFC with communication delays. The authors [9]
discussed data communication models based on queuing theory.
The stability problem for LFC with communication delays was
studied in [10–15]. The authors [10] investigated the delay-
dependent stability of multi area LFC scheme with PI controllers
using Lyapunov-theory-based delay-dependent criterion and LMI
techniques. The authors [11] described the impact of time-delays
on small-signal angle stability of power systems which presented a
power system model based on delay differential algebraic (DDAE)
and described a general technique for computing the spectrum of
DDAE. The authors [12] analysed the delay-dependent stability of
LFC of multi area system by finding the delay margin using LMI
technique and obtaining the relationship between delay margin and
controller parameter. The authors [13] presented a criteria for
ascertaining delay-dependent stability of networked multi-area
LFC systems with feedback loop delay in the presence of unknown
and time-varying exogenous load disturbance. The authors [14]
proposed a graphical method to compute the stabilising values of
PI controller parameters for a single-area LFC system with time
delay. The authors [15] explored the delay-dependent stability for
single area power system LFC models installed with optimal
controller considering both time delay and packet dropout. For the
control of LFC with the time delay, the authors [16] discussed the
application of linear matrix inequalities for LFC with
communication delays; the authors [17] investigated the delay
dependent/independent design of H
∞
controller for LFC of two
area system. The authors [18] proposed a delay-dependent H
∞
non-
linear sliding mode controller in two-area interconnected power
system for LFC. The authors [19] designed a robust controller
based on continuous pole placement method for multi area LFC
scheme affected by communication delays. The authors [20]
proposed an LMI-based robust predictive LFC for power systems
with communication delays.
Though robust performance can be achieved using the above
proposed methods; however, they do not have a fixed structure and
are hard to tune and maintain in practice. Instead, proportional-
integral-derivative (PID) has a fixed control structure and is easier
to tune. Recently, PID-type LFC has attracted much attention. The
authors [21] proposed a PID tuning method mainly based on a
maximum peak-resonance specification for single-area power
system, and the result is extended to two robust decentralised PI
control designs for a two-area power system with time delay [22];
[10] suggested a method for the determination of PI parameters in a
broad class of linear control systems affected by time delays. The
authors [23] used an optimal H
∞
control and a mixed H
2
/H
∞
method to solve two robust decentralised PI controllers in LFC
communication delays, and to verify the method, a laboratory
experiment was conducted in [24]. The authors [25] developed a
novel delay-dependent robust method for analysis/synthesis of
PID-type LFC schemes considering the time delays introduced
from the communication networks. The authors [26–28] proposed
to tune PID load frequency controller based on two-degree-of-
freedom internal model control (IMC) technique. It was shown that
the time-domain performance and robustness of the resulting PID
controller is related to two tuning parameters, and by tuning the
two tuning parameters the method can achieve good performance
for power systems with non-reheat, reheat, and hydro turbines. By
assuming that there is no tie-line power flow among areas, the
above method can also be used to tune decentralised load
frequency controller for multi-area power systems with/without
communication delays.
In fact, to replace PID control, a control method should have the
following properties:
i. have a fixed control structure, and the structure should be easy
to implement in practice;
IET Gener. Transm. Distrib., 2018, Vol. 12 Iss. 6, pp. 1397-1403
© The Institution of Engineering and Technology 2017
1397
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