1. 12 CP0518_FF

7/25/2019 1. 12 CP0518_FF

1/4

2012 China International Conference on Electricity Distribution (CICED 2012) Shanghai, 5-6 Sep. 2012

CICED2012 Session 2 Paper No CP0518 Page1/4

The Current Situation And Development Of Active Power

Filter Technology

Xuan Hu Shibao Qian Mingjin Ding Bing Li

Guodian Nanjing Guodian Nanjing Guodian Nanjing Guodian Nanjing New

Energy

Automation Co., Ltd. Automation Co., Ltd. Automation Co., Ltd. Technology Co., Ltd.

China China China China

[email protected] [email protected] [email protected] [email protected]

AbstractWith the wide range of power electronic device

applications and the connection of new energy resources to

the electricity grid, a lot of harmonic problem will cause the

instability of the grid system, the interference and

malfunction of the other electric equipment, and affect the

safety of the power supply system and equipment operation.

This paper mainly discusses the comprehensive research

background and development situation of the APF (Active

Power Filter) technology, summarize the future development

and the market prospect.

KeywordsAPF, Harmonic Suppression, Reactive Power

Compensation

INTRODUCTION

With the development of power electronic devices and theaccess of new energy, power quality is becomingincreasingly important, the electrical equipments withnonlinear characteristics are widely used in metallurgy,steel, transportation, chemical and other industrial fields.Firstly, the high order harmonics in the grid will cause theoverheating of rotating electric machine and transformers,working improperly of power capacitor bank, or even thethermal breakdown damage. Secondly, that will causegreat harm of relay automatic devices, and energy meteringdevices, and lead to serious equipment malfunction, whichresults in a major accident. Thirdly, harmonic pollutionseriously influences the communications, computersystems, high-precision processing machinery,

instrumentation and other electrical equipment. Harmonicpollution also affected the normal production of varioustypes of large factories and mines, such as steel, coal,chemical, textile and other enterprises, as well as IT andlarge-scale microelectronic integrated circuit enterprises,with the result of product obsolescence, stopping of the

production line, life reducing and damage of theproduction equipments. Therefore, we must take effectivemeasures to eliminate harmonics in grid system.Active Power Filter (abbr. APF) is capable of harmonicsuppression dynamically, reactive power compensation,and has a better ability to adapt to the changes in load andharmonic. Following the description of the active filtertechnology background; this article undertakes a

comprehensive exposition of the technical characteristicsof the APF, the development status and marketapplications and prospects.

THETECHNICAL DEVELOPMENT OF AN ACTIVE

POWER FILTER

2.1 Technical features

There are traditional harmonic control and reactive power

compensation in passive filter. a low-pass circuit is formed

by paralleling RLC with the load, with the simple features,

but shortcomings of fixed compensation and easily

resonant, poor adaptability, bulky volume. Active power

filter shows the characteristics of fast response time,

tracking compensation of specific harmonics, small size,

not affected by system parameters, etc.. In the power

system, the main role of the APF is to reduce the harmonic

pollution and improve power quality. And APF also the

function of reactive power compensation and three-phase

equilibrium control.

After sampling the voltage and current of the

compensation object, APF output the compensation current

through computing step and power loop amplifier.

Compensation current offset the harmonic current of load

current to remove the harmonic components of the

fundamental supply current.

Nonlinear

load

is iL

ic

APF

es

Command

current

compute

Current

track

control

Drive

circuit

Figure 1 schematic of the shunt APF system

Figure 1 shows schematic of the shunt APF system.harmonic sources is the power load, which generates

harmonics and reactive power consumption,Li

Si stands

for current of the load side and the network side

7/25/2019 1. 12 CP0518_FF

2/4



respectively,Ci stands for compensating current of the

active filter.

2.2 Major categories of active power filter

Seried-type

Parallelled-

type

Unified Power Quality

Conditioner

independent

hybrid Seried

type

independent

Parallel hybrid

type

Injection circuit

mode

Series resonant

Parallel resonanthybrid type

A

P

F

Figure 2 Active Power Filter Category

2.2.1 The way of access to the gridAccording to the way of access to the grid, the active

power filter can be divided into three categories: series-

type, parallel-type and mixed-type.[4]

Shown in Figure 3a, the series-type active power filter can

be equivalent to a controlled voltage source. With thecoupling transformer stringing into the power supplysystem, the series-type active power filter is to eliminatethe voltage harmonic. Compared with shunt active powerfilters, series active power filter has shortcomings such as

big loss, switching, uneasy to exit and the complexity ofthe various protections.

Currently series-type active power filter form the serieshybrid active power filter in combination with the LC

passive filter.Shown in Figure 3b, shunt active power filter can beequivalent to a controlled current source. with the systemin parallel,. The shunt active power filter is used forharmonic compensation current source inductive load, withthe advantages of the less power loss, switchingconveniently, flexible and simple protection. That is quitemature technically; and active power filter has been put

into use in the industrial application.[1]

When shunt active power filter is applied to filter out theharmonic separately, there are request of large amount ofcapacity requires. And that will bring a range of issues,

such as high cost, electromagnetic interference, complexstructure and higher power loss.

Nonlinear

load

us uc uL

APF

es

aSeries-type APF

Nonlinear

load

is iL

ic

APF

es

bShunt APF

Figure 3 the basic topology of APF application

The hybrid parallel APF and PF type is shown in Figure 4a,the hybrid series APF and PF type is shown in Figure 4b,,in which parallel LC passive filter part is used to eliminatea large number of low order harmonics, so the capacity ofthe active filter part can be very small, and the size andcost of the active filter will be greatly reduced. ButCompensation performance is not good under thecircumstances of different load or operation status changes.Series resonant injection APF and parallel resonantinjection use the impedance characteristics of the LCcircuit at the fundamental and harmonic, which apply toreactive power compensation harmonic governance.

Nonlinear

load

is iL

ic

es

PFAPF

aThe hybrid parallel APF and PF type

Nonlinear

load

APF

es

PF

is iL

ic

bthe hybrid series APF and PF type

Figure 4 the basic topology of hybrid APF application

Figure 5 shows a series parallel type of APF, also knownas the Unified Power Quality Conditioner (UPQC),composed by two structures of the series-type APF andshunt APF, which share the same DC capacitor or

inductive energy storage devices, to solve power qualityproblems. Series-type APF compensates voltage harmonics,fluctuations or flicker, while the shunt APF compensatescurrent harmonic imbalance, compensation of reactive

power load, and adjusts the DC voltage. As the ideal active

7/25/2019 1. 12 CP0518_FF

3/4



filter structures, UPQC can achieve short-termuninterruptible power supply, storage, reactive powercompensation, harmonic suppression, the elimination ofvoltage fluctuation and flicker, and maintain system

voltage stability. But for its high cost and complex ofcontrol, further study and practical application should bemade.

Nonlinear

load

is iL

ic

us uc uL

UPQC

es

Control and drive circuit

Figure 5 topology of Unified Power Quality Conditioner

2.2.2 The compensation systemaccording to the compensation system, the active filter can

be divided into single-phase, three-phase three-wire andthree-phase four-wire system.Single-phase active filter handle the load of low-power,while the converter's switching frequency can be high.Most single-phase loads are powered with the center line

of three-phase system. Single-phase power causes theproblems of neutral current harmonics, reactive and three-phase unbalance. The introduction of three-phase four-wireactive filter is to reduce this type of system problems.

HARMONICDETECTION METHODS

Response speed and detection accuracy is an importantindicator to determine the detection methods; moderndetection methods have advantages and disadvantages.There are a few commonly used detection methods shown

below. Harmonic detection method based on instantaneousreactive power theory is relatively mature, and becomesthe most widely used method.

3.1 Fourier transform-based frequency domain

analysis algorithm

The algorithm uses the fast Fourier transform (FFT) tocalculate the harmonic components. By sampling thevoltage and current signals of one cycle, and the harmonicand reactive current will come out ultimately. It is easy torealize the specific harmonic elimination, but thecalculation routine is large, and real-time can not beguaranteed. it is difficult to achieve the instantaneousdetection and compensation requirements.

3.2 Algorithm based on instantaneous reactive

power theory

Instantaneous reactive power theory is proposed by theJapanese scholar H.Akagi 1983. With The instantaneousreactive power theory, the instantaneous active power andinstantaneous reactive power of three-phase voltage and

load current are detected. By removing the fundamentalcomponent, high-order harmonic of instantaneous active

power and instantaneous reactive power is computed, andthe required compensation current instruction value will be

calculated. Although the method is able to trackcompensation current fast and timely, but because ofdigital low-pass filter, there will be some delay, and thedetection accuracy is not high.There are other detection methods, such as neural networklearning algorithm and the wavelet analysis method, but

because of the complexity, its difficult to achieve practicalapplication.

CURRENTTRACK STRATEGY

4.1 Hysteresis Current Control (HCC)

Hysteresis current control is a nonlinear closed-loop

current control method and currently the most widely usedin the APF control, which forms a dead zone of a givencurrent by hysteresis comparator. The switching action ofthe PWM converter is controlled through hysteresis errorof the feedback current and command current. This methodhas the characters of simple circuit, small switching loss,fast dynamic response, but the switching frequency of thesystem response speed and current tracking accuracy isaffected by the hysteresis broadband. In addition,independent control of three phases result in phase

interference in none neutral line three-phase inverter.[2]

4.2 Triangular Carrier Control (TCC)

The triangle carrier PWM is one of the most simple linear

control method, which scales difference between the APFoutput current and command current, and output PWMswitching control signal by high frequency triangularcarrier modulation so as to obtain compensation current.The advantages of this method are the stability of theswitching frequency, fast response, and good controlcharacteristics in high-frequency switching system. The

disadvantage is more switching losses.[8]

4.3 One-Cycle Control(OCC)

One cycle control method is a generic non-linear large-signal control method, and particularly suitable for thecontrol of the switching circuit. The basic idea is to controlthe duty cycle of the switch in each period, make the

average of the switch variable equal or proportional to thereference signal, and thereby eliminate the steady andtransient errors. It has a fast response, high precisioncontrol, simple control circuit, robust. The disadvantage iseasily affected by circuit changes in working conditions.

4.4 Dead-Beat Control (DBC)

The method is actually a pre control, and the basic idea isto calculate the switch control to the next sampling period

by the load current and compensation current in theprevious sampling period. The advantages are fast dynamicresponse, and easy software implementation, thedisadvantages are the amount of calculation anddependence on the system parameters.

In addition to the introduction of a variety of currenttracking control strategy, there are many modern controlmethods, such as Sliding Mode Control (SMC), SpaceVector Control (SVC), etc.. Application of active powerfilter control algorithm should be based on the harmonic

7/25/2019 1. 12 CP0518_FF

4/4



situation, considering the control accuracy, response speed,the system immunity factors.

RESEARCH OF ACTIVE POWER FILTER

Now, with the widely application of nonlinear loads on theuser side, market demand for utility grid security, electricalequipment reliability is growing more over. As an effectiveharmonic suppression and compensation devices, theapplication of active power filter will be increasingly moreextensive.Active Power Filter technology researches focus on thecontrol method. With the rapid development of computertechnology, more research and application by moderncontrol methods will be deeper. We need to consider thefollowing direction of the research in the APF:

(1) The establishment of a reliable and stable algorithmmodel in-depth study;

(2) To improve the dynamic performance and theresponse of harmonic compensation in the APF;(3) Study the applicable control methods in harmonic

characteristics from different compensation objects.

CONCLUSION

Active power filter can effectively improve the powerquality, reduce the harmonic absorption of reactive power,and improve the stability of equipment operation. With thewidely applications of multiple energy forms and converterequipment, APF relates to various industrial fields, and themarket prospect is broad. With further promotion, theactive power filter industry will be better and better.

REFERENCES

[1] Zhanying Li, Zhen Ren, Zeming Yang, 2004, "Survey On Active

Power Filter Devices And Their Application Study", Power System

Technology, vol. 28, No.22., 40-43

[2] Wenying Xiao, Zhongxian Zhang, 2006, "Active Power Filter

Technology and Development", China Technology Information, vol.

8, 88-89.

[3] Rusong Hu, 2003, "High Frequency Control energy", China Electric

Power, Vol. 36.

[4] Shan Zhong, Yang Sheng, Zhenming Zhao, 2011, "Technology and

Development Review of Active Power Filter", Inverter World, Vol.

1, 45-49.

[5] J H Marks T C Green Predictive control of active power

filtersPower E1ectronic and Variable Speed Drive2000

9(5)1823

[6] Z LuT GreenNeural network based predictive control strategy of

active power fi1ter for electric drivesIEE PEVD 2002

7(456)287-291

[7] Xiangning Xiao, Yonghai XuWu LiuAnalysis Of Hybrid PowerCompensator And Its Experimental Study. Automation Of Electric

Power Systems, 2002, 26(5), 39-44

[8] Chaobo Dat, Haixue Lin. A Novel Triangular Carrier Current

Control For Voltage Source Inverters.Proceedings of the Csee, 2002,

22(2), 99-102

[9] Guozhu Chen, Zhengyu Lu, Zhaoming Qian. The General Principle

Of Active Filter And Its Application. Proceedings of the Csee

2000,20(9)17-21

[10] Xiaoqing YanZhaoan WangThe Study of How the Control

Methods of Shunt Active Power Filter Affect Its Dynamic

Characteristics.Journal Of Xi An Jiaotong University, 1998, 32(6),

2630

1. 12 CP0518_FF

Documents

Transcript of 1. 12 CP0518_FF