Energy and Power Engineering, 2013, 5, 1215-1220
doi:10.4236/epe.2013.54B230 Published Online July 2013 (
The Development of Network based Composite Power
quality Regulation Device
Weiqiang Fan, Ying Lei, Jing Zhu, Luo Li, Shuai Niu
New energy technology research department, Xi’an High Voltage Apparatus Research Institute Co. Ltd, Xi’an, China
Received March, 2013
First, the paper analyzes the advantages and disadvantages of all kinds of reactive power compensation technology, and
then proposes a principle and integrated control strategy of the composite operation of TSC and SVG, also the paper
designs and develops the main co ntroller of Network based composite power qu ality regulatio n device, based on RTDS,
the real-time digital simulation model of The Device is established, and finally the prototype of the device is developed
with the function of filter and split-phase compensation. The main controller determines the cooperative operation of
both TSC and SVG, and the switching strategy of TSC. The simulation result in RTDS can verify the precision of the
measure system and the validity of the control logic, the prototype has finished the type test according to the national
Keywords: Network Based; Composite Power Quality Regulation Device; Reactive Power Compensation Technology;
1. Introduction
With the rapid development of national economythe
amount and variety of power consumption equipment
connected to the distribution network are also increasing,
which causes the growing decline in the power quality
characterized by the large amount of reactive power and
serious harmonic pollution, so the effective method in
improving power quality is to adopt reactive power
compensation technology and harmonic suppression
technology [1,2].
After decades of development, a variety of reactive
power compensation devices have emerged. The cost and
technical content of MSC is low but its poor dynamic
compensation effect may bring many negative influence
behind; The advantage of TSC is low cost, the sin-
gle-tuned filter, large compensation capacity, split-phase
compensation etc, but it can only achieve the step regula-
tion of reactive power but cannot suppress voltage flicker;
The TCR+FC type has the dynamic and smooth regulat-
ing characteristics, but it can produce large harmonics
and the grid voltage have a impact on its compensation
capacity, which usually cause high fault rate. The SVG
can realize continuous reactive compensation and sup-
press voltage flicker, but its disadvantages lie in high
cost and high-power switch device’s impact on its com-
pensation capacity [3-5 ].
Xi’an High Voltage Apparatus Research Institute Co.
Ltd has developed a novel via compensator——Network
based composite power quality regulation device, which
consists of several TSC banks and a SVG, by making fu ll
use of TSC’s long-term stable reactive power compensa-
tion and power harmonic suppression and SVG’s instant
fast reactive pow er compensation, the r apidly continuous
large-capacity reactive compensation can be realized, so
this device not only compensates the reactive power and
harmonic but also has a high performance price ratio
compared to counterpart device.
2. Device Function Requirement and
Construction Principle Design
2.1. Function Requirement
In order to improve power factor more effectively and
stabilize grid voltage, and then improve the grid power
quality, The Device should have following basic func-
1) Dynamically continuous reactive power compensa-
tion, the power factor is always close to 1 when the de-
vice’s capacity meets the demands.
2) The function of specific harmonic filter, the
grid-side harmonic current injected by user can meet
national harmonic standard when the device’s capacity
meets the demands.
3) The ability to compensate unbalanced three-phase
reactive power (split-phase compensation).
Copyright © 2013 SciRes. EPE
4) The function of over-current, over-voltage, voltage-
absent, under-voltage, phase-loss etc, protections and
SVG’s self-start.
5) The function of temperature controlled protection.
6) Equipped the intelligent human-computer terminal
deviceit can measure and display voltage, active power,
reactive power, power factor and the operation state of
SVG and TSC bank.
7) Equipped the field bus communication interface, it
can achieve remote monitoring function.
The Device is mainly used in the industrial enterprise
of low voltage distribution power system, it can com-
pensate load reactive power, enhance the grid power
factor, stabilize the grid voltage, at the same time reduce
the harmonic current injected into the grid, with the in-
tention of grid energy-saving and improvement of power
supply quality. The Device mainly used in the following
1) The rapidly changing load involving in the distribu-
tion system. Apply TSC/SVG to compensate the rapidly
changing reactive power and suppress voltage fluctuation
and voltage flicker.
2) A large number of AC and DC mo tor speed reg ula-
tion equipment, induction-heating power supply, con-
trollable resistance furnace, single crystal furnace, elec-
troplating and electrolysis rectifier power etc involving in
the distribution system. Apply filter branch to compen-
sate rapidly changing reactive power and suppress the
3) A large number of switching power supply, com-
puter involving in the distribution system, since the elec-
tronic equipment groups generate serious harmonic in-
terference, we adopt filter branch not only to compensate
load reactive power but also to prevent grid harmonic
amplification, achieve high precision requirement of re-
active power compensation.
2.2. Principle
The Device has the advantages of low cost, rapidly con-
tinuous reactive power compensation, because it has the
function of both TSC and SVG:SVG can provide
small-scaled capacitive and inductive reactive power and
then attain the precision compensation of reactive power,
at the same time it can suppress grid voltage fluctuation,
so it is the continuous-time subsystem in the device; TSC
can provide large-scaled capacitive reactive power, ad-
justment by grades it can attain the rough compensation,
at the same time it has the advantages of split-phase
compensation, harmonic prevention in the branch series
with reactors, so it is the discrete-time subsystem in the
device; Both can operate together by the main controller
to have the advantages and disadvantages complemen-
tary of TSC and SVG, with the intention of rapidly con-
tinuous large-scaled reactive power compensation in low
The Device can attain continuous compensation be-
tween maximum capacitive reactive power and maxi-
mum inductive reactive power through the composite
operation of both TSC and SVG. When the grid-side
reactive power demand values locate between N-TSC
banks and (N+1)-TSC banks, switch N-TSC banks and
then the SVG compensates the rest reactive power de-
mands, with the intention of rapidly continuous large-
scaled reactive power compensation in low cost.
2.3. Structure Design
The basic structure of The Device is in Figure 1, N-TSC
banks and a SVG are connected to the gridthe capacity
of TSC and SVG depends on the different working con-
dition, the main controller firstly detects grid voltage,
current, then calculates present grid power(involving
active power and reactive power),after analyzing SVG’s
operation state, it finally gives the switching order to
compensate the large amount of reactive power in the
grid and ultimately improve power factor as well as
power quality.
Considering that TSC can compensate three-phase
balance or unbalanced reactive power and reactor in se-
ries with TSC branch as filter, we use some TSC as
three-phase compensation groups and the rest as spit-
phase compensation groups, and connect reactors sepa-
rately in series with TSC branch to filter harmonics. In
the way, The Device has the function of three-phase
compensation, spilt-phase compensation, filter, harmonic
prevention etc.
3. The Main Controller Design
3.1. Functional Design
According to the system structure of The Device, the
main controller has following feature to ensure proper
Figure 1. The structure diagram.
Copyright © 2013 SciRes. EPE
W. Q. FAN ET AL. 1217
1) Detect three-phase voltage and current in the grid
and then calculate present active power, reactive power
and power factor.
2) Properly communicate with SVG, TSC controllable
chips, inquire SVG and TSC present state and then dis-
play to the user.
3) Correctly give TSC switching order according to
the defined workflow, reduce the reactive power supply
as low as possible and improve power factor.
4) Equip the intelligent human-computer interface of
the exchange, can modify operation mode and some
functional data, and external communication mode in-
cluding CAN, RS232 and RS485 etc.
The main controller consists of controlled chip and
display terminal. Figure 2 is the function diagram of the
main controller designed in the paper: it firstly realizes
the sampling of voltage, current, temperature, then cal-
culates present reactive power, active power in the grid,
finally gets the TSC switching order after analysis; The
main controlled can prop erly communicate with TSC and
SVG, and then give order to them. It can communicate
with touch screen and display present operation state;
also it can instruct present operation state through I/O
3.2. Man-Computer Interface Design
The touch screen is the man-computer interface of total
system and play an important role in the syste m .For one
thing, the touch screen can display the operation state of
total system, then it provide user with grid voltage, active
power, reactive power, power factor, TSC switching state
and SVG operation state etc. when the device is runn ing.
For another, it is convenient for the user to control the
operation state of every module through touch screen;
also the user can do the TSC switching, SVG’s start-stop
setting and parameter setting in the touch screen as re-
As shown in Figure 3, the main controller firstly sam-
ples the grid voltage, current, based on the instantaneous
reactive power theory, it calculates active power and re-
active power of every phase in the grid, then after TSC
split-phase, three-phase compensation strategy analysis,
it concludes the TSC switching results, finally it sends
the order to the TSC banks through communication in-
terface and completes the TSC switching operation. In
this way, the controller not only can finish intelligent
switching control but also instruct the SVG to compen-
sate the rest reactive power in the grid.
4. Test
According to the national standard, the composite power
quality regulation device completes the type test. The
device is shown in Figure 4
4.1. Inrush Current Test
Figure 5 is the inrush current test wave recorder meas-
ured by the oscilloscope when the capacitor switches in
the TSC branch. When the TSC receives the switching
order, it switches at the UT(the voltage between thyris-
tor’s A anode and K cathode) zero-crossing instant, the
maximum inrush current peak value is about 75 A, and
the steady-state value is about 50 A, the inrush current
value is about two times of the steady-state value.
Figure 2. The function diagram of main controller.
Figure 3. The flow chart.
Figure 4. Network based Composite Power quality Regula-
tion Device.
Copyright © 2013 SciRes. EPE
Figure 5. TSC Inrush current test.
4.2. Main Controller Test
The test is the composite compensation functional test of
both TSC and SVC branch, The Device’s model is
established in the RTDS system, when the reactive power
of the load varies within device’s capacity, the main
controller regulates both TSC banks and SVG to work
together harmoniously, which can make The Device’s
rapidly continuous compensation possible and at the
same time improve the power factor as well as power
In the process of the test, by changing the reactive
power of the load, we observe the TSC banks switching
changes, the reactive power generated by SVG and the
composite compensation effect.
4.2.1. Experimental Results of Three-phase Balanced
Load System
The simulated waveform is shown in Figure 6 when the
TSC was in the under compensation state. When the in-
ductive load attained 50kvar, TSC banks were switched
on, and T SC current and SVG cu rrent remained in phase
which lead the grid voltage by 90 degrees, then the TSC
was put into undercompensated operation while th e SVG
generated capacitive reactive power; after compensation,
grid current and grid voltage were in phase and the pow-
er factor attained 1.00.
Note: the waveform from top to bottom are grid volt-
age, grid current, TSC branch current, SVG current out-
put respectively.
The simulated waveform is shown in Figure 7 when
the TSC was in the overcompensation state. When the
inductive load attained 80k var, TSC banks were switched
on, and TSC current and SVG current were of the oppo-
site phase, TSC current led the grid voltage by 90 de-
grees while SVG current lagged the gird voltage by 90
degrees, then the TSC was put into overcompensated
operation while the SVG generated inductive reactive
power; after composite compensation, grid current and
grid voltage were in phase and the power factor attained
The composite compensation functional experiments
above have verified that the main controller can effect-
tively cooperate and control the composite compensation
of both TSC and SVG and ultimately attain the optimal
compensation effect.
4.2.2. Experimental Results of Three-phase
Unbalanced Load System
The experiment can assess the function that main
controller automatically switch on-off the spilt-phase
compensated capacitor branch of TSC under unbalanced
load system, in the process of simulation, we can adjust
the unbalanced load as required and observe the spilt-
phase compensation capacitor’s switching state accord-
ing to the every single-phase loads, at the same time
calculate the degree of unbalancedness of the system.
The unbalanced loads had a limited impact on the grid
voltage because of the large power supply capacity, in
the test we adopted the current unbalanced level which
are defined by the formula in the IEEE Std.936-1987, as
follows: using mean value of three-phase current, the
three-phase voltage unbalance level can be expressed by:
% 100%
abc abc
Figure 6. The simulated waveform when the TSC was put
into undercompensated operation.
Figure 7. The simulated waveform when the TSC was put
into overcompensated operation.
Copyright © 2013 SciRes. EPE
W. Q. FAN ET AL. 1219
Table 1. Data sheet of TSC split-phase compensation test.
Note: A1 represents the first unbalanced load group in A-phase, B1 repre-
sents the first unbalanced load group in B-phase, A2 represents the second
unbalanced load group in A-phase, the three current values represent the
current in the A,B,C phase respectively.
Table 2. Data sheet of power supply harmonic.
Then the three-phase current unbalanced level can be
expressed b y :
max( ,,) min( ,,)
abc abc
As shown in the Table 1, we can see that when the
un-balanced load occurred in the grid, the main controller
can give TSC spilt-phase compensation units switching
order according to the TSC’s switching state and drasti-
cally reduce the current unbalanced level, with th e inten-
tion of unbalanced compensation of The Device.
4.2.3. Fi lter Test
Reactors are connected in series with the capacitors in
the TSC branch to compose the filter, but it can only fil-
ter certain times harmonic, we take the fifth harmonic for
example, Table 2 shows the rest harmonic current in the
grid when the fifth harmonic with the current of 40.7 A
was injected in the grid and two-TSC banks were
switched on. We can see from the table that after two
units TSC’s switching, the rest harmonic current in the
grid is 14.37 A and the harmonic suppression rate attains
to 64.70%, at the same time the test can verify the filter
functio n o f The Device.
5. Conclusions
The Device is a multifunctional compensation device
with a high cost-performance rate, the field test and si-
mulation in the RTDS system can verify that the device
can realize the rapidly continuous reactive power com-
pensation, at the same time has the ability to co mpensate
unbalanced load, filter and harmonic prevention, so it is
worth popularizing to improve power factor and power
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