Download Design and Implement Harmonics Injection Source for Voltage

2016 China International Conference on Electricity Distribution (CICED 2016)
Xi’an, 10-13 Aug, 2016
Design and Implement Harmonics Injection Source for
Voltage Measurement Transducer
Guo Liwei
Guangdong Power Grid Corporation Communication Company
Abstract—Nowadays, the fast rising of the industries
and the power system development cause the
harmonic source increasing. More and more high
orders and power harmonic is injecting into the power
system, which may cause equipments damage. The
equipment has to be test whether its quality and
performance is enough reliable when harmonic is
existing at operating. Therefore, the harmonic
injection method is used as the harmonic test bed.
A new harmonic test bed is be proposal in the paper
and implemented harmonic range from 100Hz to
5000Hz in High voltage laboratory. The new harmonic
injection method is separately injection the harmonic
source and the fundamental main supply via different
step-up transformer. And the filter is designed and
installed at the harmonic side in order to block the
fundamental frequency which may cause the negative
effect to the power amplifier.
Index Terms—Power Quality, Reliability, Harmonic
I. INTRODUCTION
With the development of the power system, the
modern equipments, such as communication systems
and electronic equipment would be disturbed not only
by power interruption or voltage sag, but also the
distorted voltage or current source [1]. Although the
concept of power quality is introduced at early 1990s,
the interest of the harmonics becomes the key issue in
recently year.
As the definition of Harmonics, it is a periodic
sinusoidal waveform having a frequency that is an
integer multiple of a fundamental frequency (50Hz or
60Hz). [2] In power system, the waveform is expected
as perfectly sinusoidal wave at rated voltage and one
specific system frequency (50Hz or 60Hz). However,
different kinds of power electronic equipment and
sources, which built in the power system, cause the
‘pollution’ to the network [3]. As the harmonic
propagation cannot be eliminated spontaneously,
relevant suppression equipment has to be installed.
The relevant equipment is expensive so that increases
investment cost. The impact of harmonics is extremely
harmful to the grid. For example, Capacitor or
transformer would fail because of the resonance,
overheating the transformers and motors causes low
efficiency, the protection devices would maloperate
and so on [3]. Therefore, the aim of the harmonics
CICED2016 Session 2
Paper No CP0842
measurement in industry is verifying the compliance
with the harmonic distortion requirement and
investigating flawed design. Monitoring and
measurement of the harmonics is necessarily
considered in the power system operation. According
to IEEE Standard 519 [4], the harmonic measurement
should be taken up to 50th harmonics. However, it is
required 100th harmonics in some industry customers.
For monitoring and measurement of harmonics, the
harmonic source designs can be classified as 3 types.
First one is single power source [7], which is the
source generation both fundamental and different
orders frequencies. And the output signal is amplified
by the power amplifier to the desired power. The
signal can be directly injected to the test object.
Second one is combined power source with main
supply and harmonic generation [8] [9]. And there are
two filters to block unwanted signals, one is located at
the main source side to block harmonic signal and
another one is located at harmonic side to block the
fundamental signal. The main power and the harmonic
generation are superimposed and injected into the test
objective directly or via the step-up transformer. In the
previous two designs, both of the main supply and
harmonic injection way is either directly inject or use
step-up transformer.
There is a new design, which is separately located the
main supply and the harmonic source by the step-up
transformer. The main supply rises to the desired
voltage level by the step-up transformer. And the
harmonic source is amplified by power amplifier to
desired power. This design is given another way to
injection the harmonic to measurement the frequency
response of the test object.
II. PROPOSAL AND DESIGN OF THE HARMONIC
INJECTION SOURCE
A. Review the existing Test Rig
The Medium Voltage Transducer Frequency Response
Test bed was built in the high voltage laboratory. As
Fig.1 shown, the test bed consists of Power Source, the
High Voltage Reference, the VT test object and the
data acquisition system.
Page /5
2016 China International Conference on Electricity Distribution (CICED 2016)
Fig.1 block diagram of frequency response test bed
Step-Up
Transfor
mer
Power
Source
HV
Referenc
e
VT Test
Object
Data Acquisition
System
PC
This test bed was used to do tests of the 33kV wound
voltage transformer. PC generates the combined signal
with fundamental and harmonic by controlled
PCI-6251[10]. And the signal is amplified to desired
level by a power amplifier. And there are two resistors
R1 and R2. The R1is used as a bridge resistor that
ensures the amplifier can output maximum power. And
R2 is used as stabilizer.
Next, the amplified signal is step up to the desired
voltage level of the test object via the step-up
transformer. The high voltage reference, North Star
VD-60 [10], provides a reference voltage of the
secondary side of the step-up transformer which also is
the primary side of the test object. Finally, the
reference of high voltage and response of the
transformer is recorded by the PCI-6251. The
PCI-6251 works as control system for the generation
and data acquisition system.
The test bed can inject 1% smooth harmonic at the
high voltage for all harmonic range from 100Hz to
5000Hz. And the new injection method is based on
this existing test bed.
B. Proposal and Design
As mentioned at previous chapter, the single power
source, which contains with both fundamental and
harmonic signal, via power amplifier and injection
through one step-up transformer, is used in the existing
test rig. Therefore, the new harmonic injection method
is based on the existing test rig. The configuration of
new injection method is shown as Fig. 2.
Fig.2 the proposal test bed
HV Reference
50Hz Main Supply
From PC
AMP
Load
V2
V1
ST1
WVT
V3
High Pass Filter
AMP
Main supply Side
V4
Harmonic Supply from PC
ST2
Harmonic Side
DAQ Device
PC
the fundamental signal and the harmonic signal
separately inject into the system. The main supply and
the harmonic supply are parallel connection. And there
are two amplifiers connected with both of sources in
order to amplify the signal to the required power level.
And the amplified signals are step up by voltage
transformers which are located at the main supply side
and the harmonic side separately.
In order to avoid the amplifier break down by the large
current, a high pass filter is designed to give infinite
impedance at 50Hz to block the fundamental signal so
that the power of main supply can flow into the test
object. At the same time, it gives low impedance for
CICED2016 Session 2
Paper No CP0842
Xi’an, 10-13 Aug, 2016
harmonic supply to let harmonic power inject into the
test object. Whether the new harmonic injection
method gives a better or a worse performance than the
original test rig is depends on the high pass filter
performance.
The reason why it is not necessary to install a low pass
filter at the main supply side is the step-up transformer
performs as a low pass filter in the system. The
harmonic power consumes on both the harmonic side
and main supply side transformers. The effect on the
main supply side components is weak from the
harmonic power.
C Simulation of the High Pass Filter
As mentioned previously, the load impendence is
nonlinear in the system. In addition, the simulation
model of step-up transformer and the WVT are not
enough accurate while the computational complexity
is difficult. Therefore, the simulation is roughly tuning
the value of the filter.
The tuning aiming performance is listed as follow
Step.1.According to the superposition, the main supply
is supping rating voltage, V1, voltage on the burden.
Tuning the value of the filter, till the V3, is lower than
1V and the current, I, is very small when connected a
small burden at the harmonic side, which is seem the
voltage source as a short circuit with a small internal
resistance, which means the filter blocks the 50Hz
fundamental frequency. Thus, there is no negative
effect for the amplifier at the harmonic side.
Step.2.Short circuit the main supply and connected a
small burden. The harmonic supply injects 1V at
whole frequency range from second order to one
hundredth orders (100Hz to 5000Hz) into the network.
Tuning the filter, till the voltage at the HV reference,
V2, can show an acceptable quantity of the harmonic
power injected into the test object. And the harmonic
voltage at the main supply side, V1, should keep at a
very low voltage level.
Step.3.Keep tuning the filter leads the frequency
response of High voltage reference side to smooth and
balance the cost of the filter components and the
performance.
D High Pass Filter Simulation Results
In the simulation, the third order filter has following
advantages
1 Much better attenuation at fundamental frequency
50Hz.
2.Three peak values in the V2 frequency response
make the injection power lower from 300Hz to
2000Hz.
3.Smooth frequency response with the resistor
installed.
The values of components are fixed. The filter circuit
diagram is shown in Fig.3 and parameter of
components are listed in TABLE 1
Page /5
2016 China International Conference on Electricity Distribution (CICED 2016)
transformer and the amplifier.
The C1 is parallel connection by two 20uF capacitors
each side. And the C3 is parallel connection by four
20uF capacitors each side. The circuit diagram and the
actual filter are shown in Fig.6
Fig 3 the filter circuit diagram
C1
C3
L2
Main supply
side
Xi’an, 10-13 Aug, 2016
Harmonic
injection side
Rr
Fig.6 he circuit diagram of ST and filter and the actual filter and ST
TABLE 1 the filter parameters
C1
L2
C3
Rr
20uF
1mH
40uF
1Ω
A．The System
According to the proposed design of the harmonic
branch, the whole Voltage transducer frequency
response test bed was implemented in the HV
laboratory of the University of Manchester. The
harmonic branch consists of harmonic source, the
power amplifier, the high pass filter and the step-up
transformer. The whole block diagram is shown in Fig.
4.
B．Validation the performance of the High Pass Filter
The purpose of validating the high pass filter finds out
whether the filter can block the fundamental frequency
from the main supply side. In other word, the voltage
at the amplifier, caused by the main supply, is so low
that not negative effect on the amplifier. In addition,
the high pass filter can pass though acceptable voltage
level of high order harmonic injection.
The procedure of validation the performance of the
high pass filter is as similar as the tuning steps
discussed.
The circuit diagram is shown in Figure 7. Connect the
filter with the current limit resistor, the amplifier and
the harmonic source. Switch on the amplifier.
Measurement the HV side voltage, the inductor
voltage and the amplifier voltage.
Fig. 4 the circuit diagram of whole system
Fig.7 The circuit diagram of filter performance
III. IMPLEMENTATION THE HARMONIC
INJECTION SOURCE
HV Reference
50Hz Main Supply
From PC
Load
V2
V1
ST1
V4
WVT
L2
AMP
VLV C1 Vm
C3
Rr
V3
HS
ST2
DAQ Device
PC
The configuration of the Harmonic supply is similar
as the power source in the existing system. It consists
of a Harmonic Source (supply by PC and share
channel with the main supply), an EP2500, and two
resistors R1 and R2. The circuit diagram of the power
source and the actual power source.
Injection fixed harmonic level 0.1% from the
harmonic side into the system. Validation the harmonic
can be measured at the high voltage side with an
acceptable level. And the injection level in order to
keep 1% harmonic level into the high voltage side is
calculated.
Fig.5 the circuit diagram of harmonic source and the actual power
source
Fig.8 Injection 0.1% from harmonic source
Although, the VLP2500 amplifier only is amplify the
harmonic source not both of fundamental frequency
and harmonic. As the diagram shown, the circuit is
balance circuit. The R1 and the R2 is current limit
resistor, which make sure no tripping the amplifier
protection by high current.
The 3rd order high pass filter is designed as balance
circuit in order to fit the voltage injection circuit. The
filter is installed middle of the second step-up
CICED2016 Session 2
Paper No CP0842
As the Figure shown, the highest harmonic level is
2.56% at 34th order harmonic (1700Hz). The smallest
harmonic level is 0.01% at 2nd order harmonic
(100Hz). However, the first four order harmonic is not
in consideration as the chapter 3 mentioned that the
high pass filter blocked the low frequency signals. So
the smallest harmonic level is 0.14% at the 100th order
harmonic (5000Hz). It proves the high pass filter is
working as expected and the performance is
acceptable. It means there is 10% of the high order
harmonic power can be injected into the high voltage
Page /5
2016 China International Conference on Electricity Distribution (CICED 2016)
side. The high order harmonic power is absorbed by
the step-up transformer.
C．The determination steps of the voltage injection
level at the harmonic side
The voltages mention in the equations is represented
as the normalized voltage, which is calculated by
Equation 1
V
NormanizedVoltage 
V_50Hz
Injection fixed the harmonic level, V3_fixed, from the
harmonic source. Measurement and record the voltage
V2 at the high voltage side. The recorded data will be
extracted the different order value by FFT in Matlab
programming.
According to the spectrum of V2, the transfer function
(TF) between the V2 and V3 at whole frequency range
from 50Hz to 5000Hz is calculated by Equation 2.
V
NormanizedVoltage 
Xi’an, 10-13 Aug, 2016
the result of the existing system.
The case is to test the balance configuration filter
whether can be injected desired level harmonic from
100Hz to 5000Hz. and the harmonic injection is
sustaining 0.4 second. As mention in chapter 4, the
fixed level harmonic 0.1% is injected from the
harmonic side into the system. And according to the
V2 spectrum, the voltage injection level is calculated
in order to keep 1% harmonic at the HV side. The
spectrum of harmonic injection at harmonic side is
shown and the measured harmonic is shown in Figure
9.
Fig.9 the spectrum of harmonic injection at Harmonic source and
the spectrum of measured harmonic at HV side
V3_fixed
It is expected keeping 1% harmonic level at the high
voltage side. The corresponding harmonic injection is
calculated by Equation 3.
（1%）
TF
Reinjection according to the spectrum of harmonic
injection. Measurement and record the voltage at high
voltage side V2 and the test object side V4.
NormanizedVoltage 
It was expected smooth 0.7% level of harmonic
injection at the HV side of the test bed for all
harmonic. However, it is only 0.4% level of harmonic
injection at the HV side at 5000Hz and it is more than
1% level of harmonic at around 1050Hz. The injection
spectrum has to be recalculated based on the result,
which is shown in Figure 10.
Fig.10 Reinjection spectrum of harmonic injection at the harmonic
source and spectrum of measured smooth harmonic at HV side
IV. TEST AND COMPARISON OF THE NEW
INJECTION METHOD AND RESULTS
DISCUSSION
The ultimate goal of this project is develop a new
injection method, which is the harmonic source
injection from another step-up transformer. And the
test bed can injection 1% harmonic into the test object
and get the frequency response The fundamental
frequency 50Hz and the harmonic signal from 100Hz
to 5000Hz (2nd order to 100th order) are generated by
the PC via PCI-6251 by two different channel. The
50Hz signal is amplified by EP2500 at channel 1 to
desired level (main voltage is 63.5rms). The harmonic
signal is amplified by VLP2500 at channel 2. And the
VLP2500 is set at a suitable amplify level. Both
signals are injected into the network by each side
transformer and superimposed at the high voltage side.
And the HV reference voltage V2 and the 33kV WVT
output V4 is measurement and recorded..
And the frequency response is shown by the voltage
ratio between its secondary side voltage (V4) and the
primary side voltage (V2), and it is calculated by
Equation 4 as below.
Nomanized _ voltage _ ratio 
As the Fig.10 shown, the percentage of harmonic
injection at the harmonic side is higher than the first
time, especially, the high order harmonic orders. It has
to injection 120% of harmonic at the harmonic side in
order to keep 1% harmonic at high voltage side.
However, the smooth 0.7% harmonic level is obtained
at the high voltage side. There is resonance around the
1050Hz which causes the harmonic level is higher
than others. In a word, this method used for the
harmonic injection is confirmed by the results
As the mention at the introduction, the test bed is used
for the test object frequency response. The response is
compared with the existing system shown and the
differences between the new method and the existing
system is shown in Fig.11.
V4
V2_50Hz
×
V2
V4_50Hz
In the case studies, the result will be compared with
CICED2016 Session 2
Paper No CP0842
Page /5
2016 China International Conference on Electricity Distribution (CICED 2016)
Fig.11 frequency response and the difference and the
existing system
As the Figure 11 shown, there is no significant
difference between the no-smooth injection and the
existing system except the first few orders. However,
there is significant difference between the smooth
injection and the existing system at high order
harmonic. The frequency response of the smooth
injection is little higher, 5%, than the existing system.
The reasons may cause this problem is listed in below:
1. The configuration of filters
2. The capacitor is unstable when it is operating at
high voltage and high frequency
3. the charge or the discharge is not stable when the
data is collected
4. The environment effect
V. Conclusions
The new harmonic injection method, injection
harmonic and main supply separately, is implemented
and validation. The harmonic injection is proved by
the results, which is shown that the injection is
successful and controllable. However, the accuracy of
this method is not ideally as expected when the
frequency response of the test object is measure.
The frequency response of this injection method is
higher compared with the existing system, which may
be caused by the operation environment. And the
harmonic injection is not enough stable, which may be
caused by the quality of the capacitance. It is changing
the capacitance when the voltage is varying. Moreover,
the injection power is too high at the 100th order
harmonic in order to keep 1% harmonic level at the
high voltage side.
Besides, this method may be improved by the
following further research:
1. Better quality capacitor which has a stable value at
the high voltage condition
2. Given much space between the isolation cage and
the equipment.
3. Increase the value of C3 which can change the
self-impulse of the filter and decrease the injection
power at high order harmonic.
Xi’an, 10-13 Aug, 2016
ter.
[4]Recommendation Practices and Requirements for Harmonic
Control in Electric Power Systems,IEEE Std.519-1992,1992
[5]IEC 61000-4-7 (1993), Electromagnetic compatibility (EMC) –
Part 4-7:Testing and measurement techniques – General guide on
harmonics and interhamonic measurements and instrumentation for
power supply systems and equipment connected thereto.
[6]IEC 61000-4-30 (2008), Electromagnetic compatibility (EMC) –
Part 4-30: Testing and measurement techniques –Power quality
measurement methods.
[7] M.I.Samesima,J.C. de Oliveria and E.M.Dias,”Frequency
response analysis and modeling of measurement transformers under
distorted current and voltage supply ” IEEE Transaction on Power
Delivery,vol.6,No.4,Oct 1991.
[8] L. Cristaldi,A Ferrero and R.Ottoboni, “A VI-Based Equipment
for the frequency-Domain Characterization of Voltage
Transformers”, IEEE Instrumentation and Measurement Technology
Conference,May,1997
[9] M.Tanaskovic,A Nabi, and S.Misur, “Coupling Capacitor
Voltage Transformer as Harmonic distortion Monitoring Devices in
Transmission Systems”, International Conference on Power Systems
transien, paper Bo.IPST05-031,2005
[10] M series user manual. Han 15,2009.[Online]. Available:
http://www.ni.com/pdf/manuals/371022k.pdf.
Guo liwei was born in China, in 1987. Received the B.Sc. degree in
Electrical and electronic Engineering from University of
Strathclyde , the M.Sc. degree in Power System Engineering from
University of Manchester. Currently working at Guangdong Power
Grid Corporation Communication Company.
Contact Number : 0086-13925025612
Contact Email: [email protected]
REFERENCES
[1] “Power quality measurement”. [Online]. Available:
http://ww.allaboutcircuits.com/vol_2/chpt_12/4.html.
[2]J.Arrillaga,N.R.Watson,”Power System Harmonics”,2nd ed. New
York,John Wiley and Sons 2003
[3]PQ Course Brochure Manchester. [Online].Available:
http://www.scribd.com/doc/24804266/PQ-course-brochure-manches
CICED2016 Session 2
Paper No CP0842
Page /5