Sliding mode control of a shunt hybrid active power filter based on the
inverse system method
Wei Lu
⇑
, Chunwen Li, Changbo Xu
Department of Automation, Tsinghua University, Beijing 100084, China
article info
Article history:
Received 17 January 2013
Received in revised form 12 September 2013
Accepted 25 November 2013
Keywords:
Harmonics
Hybrid active power filter
Sliding mode control
Inverse system method
Zero dynamics
abstract
In this paper, an inverse system method based sliding mode control strategy is proposed for the shunt
hybrid active power filter (SHAPF) to enhance the harmonic elimination performance. Based on the
inverse system method, the d-axis and q-axis current dynamics of the SHAPF system are firstly linearized
and decoupled into two pseudolinear subsystems. Then a sliding mode controller is designed to reject the
influence of load changes and system parameter mismatches on the system stability and performance. It
is proved that the current dynamics are exponentially stabilized at their reference states by the control-
ler. Moreover, the stability condition of the zero dynamics of the SHAPF system is presented, showing
that the zero dynamics can be bounded by adding an appropriate DC component to the reference of
the q-axis current dynamics. Furthermore, a proportional-integral (PI) controller is employed to facilitate
the calculation of the DC component. Simulation and experimental results demonstrate the effectiveness
and reliability of the SHAPF with the proposed control strategy.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
The widespread application of power electrical devices (e.g.,
diode rectifiers) has increased the harmonic pollution in modern
power transmission/distribution systems. The harmonics gener-
ated by nonlinear loads can cause additional power losses, inter-
fere with nearby communication networks and disturb sensitive
loads [1,2]. Therefore, many international standards such as IEEE
519-1992 and IEC 61000-3-2 have been recommended to limit
the harmonic pollution.
Traditionally, low-cost passive power filters (PPFs) with high
efficiencies were widely used to eliminate the harmonics. How-
ever, the bulky PPFs only provide fixed harmonic compensation
and they detune with age [3]. These drawbacks can be overcome
by the power converter based active power filters (APFs), but they
are usually expensive and have high operating losses [4–8]. For the
sake of improving the compensation performance and reducing the
cost of the APFs, a number of topologies of hybrid active power fil-
ters (HAPFs) have been proposed [9–15]. Peng et al. proposed a
HAPF system combining a series APF and a shunt PPF [9]. In this
system, the APF endured high load currents works as a ‘‘harmonic
isolator’’ between the source and the nonlinear load. A novel
topology is proposed in [10], where the APF is connect in series
with a C-type PPF. However, an additional power supply is needed
to support the DC-link capacitor. Ref. [11] presented a combined
system of many PPFs connected in series with an APF via a match-
ing transformer. This topology might not be preferable since many
passive components are required. In particular, a novel shunt
hybrid active power filter (SHAPF), where three tuned PPFs are
connected in series with a small-rated APF without any matching
transformers, has attracted much attention [12–15]. Since the
source voltage is applied across the PPF, the required rating of
the APF can be substantially reduced. Furthermore, no additional
output filters are needed to suppress the switching ripples
produced by the power converter.
The control strategy is important to enhance the harmonic
elimination performance of the SHAPF. Many control strategies
have been proposed for the SHAPF. In [13], a linear feedback-feed-
forward controller is designed for the SHAPF. Because the dynamic
model of the SHAPF system contains multiplication terms of the
control inputs and the state variables, it is not easy to achieve both
satisfactory steady-state and transient-state performances with
the linear control strategy. To deal with the nonlinear characteris-
tic of the SHAPF, a sliding mode controller was presented in [14],
which has the property of robustness against load changes and sys-
tem parametric uncertainties. But the steady-state errors may still
be nonzero due to the absence of integrators in the closed loop sys-
tem. In [15], a Lyapunov function based control strategy is devel-
oped to globally stabilize the SHAPF system. Unfortunately,
owing to the difficulty in estimating the ripple component of the
0142-0615/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.ijepes.2013.11.044
⇑
Corresponding author. Tel.: +86 10 62799024, mobile: +86 15210958618; fax:
+86 10 62795356.
E-mail addresses: lu-w09@mails.tsinghua.edu.cn (W. Lu), lcw@mail.tsinghua.
edu.cn (C. Li), xcb07@mails.tsinghua.edu.cn (C. Xu).
Electrical Power and Energy Systems 57 (2014) 39–48
Contents lists available at ScienceDirect
Electrical Power and Energy Systems
journal homepage: www.elsevier.com/locate/ijepes