The Development of Network based Composite Power quality Regulation Device

doi:10.4236/epe.2013.54B230

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Energy and Power Engineering, 2013, 5, 1215-1220

doi:10.4236/epe.2013.54B230 Published Online July 2013 (http://www.scirp.org/journal/epe)

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

Email: [email protected]

Received March, 2013

ABSTRACT

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

standard.

Keywords: Network Based; Composite Power Quality Regulation Device; Reactive Power Compensation Technology;

RTDS

1. Introduction

With the rapid development of national economy，the

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-

tions.

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).

W. Q. FAN ET AL.

1216

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

device，it 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

situations:

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

harmonics.

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

cost[6-8].

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 grid，the 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

operation:

Figure 1. The structure diagram.

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

interface.

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-

quired.

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.

W. Q. FAN ET AL.

1218

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

quality.

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

1.00.

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:

936

max(,,)min(,,)

% 100%

abc abc

UUU UUU

PVUR U





(1)

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.

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

III III

PVIR I



100%

(2)

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

quality.

REFERENCES

[1] Z. A. Wang，J. Yang and J. J. Liu, “Harmonic Suppres-

sion and Reactive Power Compensation,” Beijing：China

Machine Press, 2005, pp.167-19．

[2] A. Luo, “Grid Harmonic Suppression and Reactive Power

Compensation Technology and Equipment,” Beijing:

China Power Press，2006, pp.183-221．

[3] Y. F. Li and Y. X. Ma, “Progress of Harmonic Suppres-

sion and Reactive Power Compensation Technology,”

Journal of Shaanxi University of Technology (Social Sci-

ences), Vol. 25, No. 1, 2009.

[4] X. Q. Tong, W. J. Wu and B. Y. Ren, “The Application

of Voltage-source Inverter in the Power System,” China

Machine Press, pp.60-63.

[5] G. F. Guo, “The Application of Reactive Power Com-

pensation in the Distribution System,” Power system

technology, Vol. 31, No. 1, 2007, pp. 229-230．

[6] Q. Gong, “TSC Dynamic Reactive Power Compensation

Technology and Its Application,” Power system technol-

ogy, Vol. 31, No. 2, 2007, pp.118-122.

[7] X. Q. Tong, Q. F. Wu and J. Yi, “The Research on the

Control Method of STATCOM in Parallel Operation,”

Journal of Xi'an University of Technology, Vol. 24, No. 4,

2008.

[8] W. Zhao and A. Luo, “The Cooperation Operation of

SVG and TSC in the System Proceeding of the CSEE

2009,” Vol. 29, No. 19, pp. 92 - 98.

[9] X. H. Ma, “Research on the DSTATCOM,” Xi'an Uni-

versity of Technology, 2004.

[10] C. B. Luo, Y. Ji and Z. Y. Liu, “The Principle and Reali-

zation of the STATCOM,” China Power Press，2005.

[11] H. S. Su and Q. Z. Li, “Rough Controlling TSC for Reac-

tivecurrent Compensation in Traction Substations,” Con-

ference Proceedings of CES/IEEE 5th International

Power Electronics andMotion Control Conference，

Shanghai，2006．

[12] H. W. Liu, “Research on the Parallel Operation of the

Active Power Filter Based on the Capacity-limited Con-

trol Strategy,” Yan Shan University, 2007.

[13] X. L. Wei and K. Dai, “The Parallel Control of Active

Power Filter in the Three-phase Three-wire System,”

Automation of Electric Power Syste ms，2007.

[14] Z. Y. Yang and J. F. Zhao and G. Q. Tang, “Research on

the Parallel Operation of the Active Power Filter Based

on the Current-limited Control Strategy,” Electric power

Automation Equipment, Vol. 3, No. 26, 2006.

[15] W. Freitas and A. Morelato and Xu Wilsun, et al., “Im-

pacts of AC Generators and DSTATCOM Devices on the

Dynamic Performance of Distribution System,” IEEE

Transactions on Power Delivery, Vol. 20, No. 2, 2005,

pp.1493-1501.doi:10.1109/TPWRD.2004.839181

[16] R. Esmaili, L. Xu and D. K. Nichols, “A New Control

Method of Permanent Magnet Generator for Maximum

Power Tracking in Wind Turbine Application,” IEEE

Power Engineering Society General Meeting, Vol. 3, No.

12-16, 2005, pp. 2090 - 2095.

[17] S. Ponnaluri, J. K. Steinke, P. Steimer, S. Reichert and B.

Buchmann, “Design Comparison and Control of Medium

W. Q. FAN ET AL.

1220

Voltage STATCOM with Novel Twin Converter Topol-

ogy,” 35th Annul IEEE Power Electronics Specialists

Conference, 2004.

[18] M. S. ElMoursi, Prof. Dr. A. M.Sharaf, “Voltage Stabili-

zation And Reactive Compensation Using A Novel

FACTS-STATCOM Scheme,” IEEE CCECE/CCGEI,

Saskatoon, May 2005.