Instrumentation & Measurement Magazine 25-5 - 11

Is It Correct that the Higher Detection
Accuracy of Single-Phase Shunt APF
Harmonic Current Detection, the More
Effective the Detection?
Zicheng Li, Mingwei Ren, Zhaoling Chen, Guohai Liu, and Dali Feng
I
s it correct that the higher the detection accuracy of a
single-phase shunt active power filter (SPSAPF) harmonic
current detection (HCD) is, the more effective the
HCD is? To answer the question, an interesting view correction
for evaluating an SPSAPF HCD is proposed in this paper.
The main points of the proposed view correction are as follows:
The answer to the question is Yes when the load current
changes periodically but No when the load current changes
non-periodically. The proposed view correction also applies
to a three-phase shunt active power filter; thus, it has general
applicability. Its existence and feasibility are confirmed by experimental
results.
Question of Harmonic Current
Detection
A significant increase in harmonic pollution has been caused
by the widespread use of power electronics devices in the
power grid. Thus, harmonic suppression has been taken more
and more seriously [1]-[3]. Usually, a power filter is employed
to restrain harmonics, and two types are used primarily, either
a passive power filter or an active power filter (APF) [4]. A
passive power filter has been widely used to compensate harmonics
because of its simplicity, high efficiency, and low cost.
However, it has some defects, including a resonance problem,
low dynamic performance, and filtering accuracy directly affected
by small parameter variations [5]. An APF is an effective
power electronics device for suppressing harmonics [2], [6];
it is classified into a shunt APF, a series APF, or a hybrid APF
[7], [8].
A shunt APF is one of the most popular APFs because of its
effectiveness, versatility, and simplicity [9]. It is divided into
a single-phase shunt APF (SPSAPF) or a three-phase shunt
APF. The function of the SPSAPF is to compensate the reactive
and harmonic currents or the harmonic currents of the single-phase
nonlinear load current [2], [10]. When the SPSAPF
compensates the reactive and harmonic currents, the function
of its reactive and harmonic current detection (RHCD) is to detect
the currents. When the SPSAPF compensates the harmonic
currents, the function of its harmonic current detection (HCD)
August 2022
is to detect the currents. In a broad sense, an SPSAPF RHCD
can also be called an SPSAPF HCD. Besides, for an SPSAPF,
its HCD gravely affects its compensation performance [2], [4],
[11], [12]; thus, harmonic current detection is one of the key SPSAPF
techniques [2], [11]-[14].
SPSAPF HCDs have so far been continually studied. Thus,
many SPSAPF HCDs have been presented [2], [4], [12], [14]-
[24], such as adaptive [15]-[17], least compensation current
[12], [14], and artificial neural network [18], [19]. Moreover,
some SPSAPF HCDs were recently published, including a
second order generalized integrator [21] and an improved
two-step ensemble empirical mode decomposition [25]. Each
of these HCDs has its own merits, whereas one or a few demerits
difficult to overcome [4], [12]. Therefore, SPSAPF HCDs will
still be continually researched.
Nowadays, a lot of literature indicates that detection accuracy
and response time are two main performance indexes for
evaluating an SPSAPF HCD. When the load current changes
periodically, the higher the detection accuracy of an SPSAPF
HCD is, the more effective the HCD is [4], [12], [14], [17]-[19].
When the load current changes non-periodically, the higher
the detection accuracy of the HCD is, the more effective the
HCD is; the shorter the response time of the HCD is, the more
effective the HCD is also [4], [12], [14], [17]-[19]. Thus, whether
the load current changes periodically or non-periodically, the
higher the detection accuracy of the HCD is, the more effective
the HCD is. This view can be considered as a dominant view
of evaluating an SPSAPF HCD. Furthermore, to determine the
states of the load current, Li et al. presented an algorithm for
recognizing them based on a dynamic iteration step [26].
Is the dominant view correct? To reply to the question, this
paper proposes an interesting view correction for evaluating
an SPSAPF HCD. The proposed view correction answers
the question and has general applicability. The rest of this
paper is organized as follows. Firstly, the three most fundamental
theoretical bases are introduced: the Fourier series of
the load current, the operating principle of the SPSAPF, and
the essential function of the SPSAPF. Secondly, a view correction
for evaluating an SPSAPF RHCD and that for evaluating
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