OPTIMAL CURRENT REGULATION STRATEGY FOR THREE-PHASE BACK-TOBACK ACTIVE POWER CONDITIONERS

International Journal of Research in Advanced Technology - IJORAT

Vol. 2, Issue 1, JANUARY 2016

1 All Rights Reserved © 2015 IJORAT

OPTIMAL CURRENT REGULATION

STRATEGY FOR THREE-PHASE BACK-TO-

BACK ACTIVE POWER CONDITIONERS M. Shunmugavidya

1, Priyanka Rajan

2, A.Ravi

3

1

Student, Dept of EEE, FRANCIS XAVIER ENGINEERING COLLEGE, Tamilnadu, India 2

Student, Dept of EEE, FRANCIS XAVIER ENGINEERING COLLEGE, Tamilnadu, India 3

Head of Dept, Dept of EEE, FRANCIS XAVIER ENGINEERING COLLEGE, Tamilnadu, India

Abstract: The objective of this paper is to propose a three phase back-to-back power conditioner with optimal a current

regulation strategy in microgrid. To achieve high stability ,the frequency and the voltage of the microgrid is controlled

by using bidirectional power flow control .The active and reactive power of Active Power Conditioner(APC) is used

here. The dc-link capacitor is the main component of the back-to-back power conditioner for power decoupling and

power flow balancing. Optimal current regulation strategy is developed to improve the power quality and stability of

the micro grids as well as to reduce the dc link capacitance. Under steady state, the optimal ac current regulation is

able to achieve the dc-link voltage regulation and to reduce the injected ac line current variation. Simulation result was

used to demonstrate the feasibility and performance of the proposed active power conditioner.

Keywords: Microgrid, Active Power Conditioner, Bidirectional Power Flow, Line current.

I.INTRODUCTION

Microgrids will play a pivotal role in solving the

energy challenges of the future. Microgrids are

autonomous grids that operate either in parallel to, or

„islanded‟ from, existing utility power grids. They

have the power to efficiently and flexibly meet the

growing energy demand of communities: whether

they are grid-connected or not .Microgrids allow for

fast installation of electricity supply without the need

for expensive transmission infrastructure investments

and the lengthy development approval and

construction process. This will especially empower

remote, non-grid-connected communities around the

world.

To limit the carbon dioxide emission, micro-grid

systems consist of distributed generators (DGs) have

been rapidly developed. The performance of the DGs

will be greatly affected by the unpredictable

environmental conditions, it will create negative

impacts to the power quality of the micro-grid. An

APC is a device connected between two micro-grids,

used to provide the capability to improve the quality

of power on both sides. When fault on one microgrid

is detected, the other microgrid can provide active

and reactive power compensation via the APC.

Hence, the APC becomes a necessary component for

the micro-grid application. Now, power converters

with back-to-back structure are used in many

applications, such as motor drivers, traction power

systems, wind power systems and micro-grid

applications. Therefore, a three-phase back-to-back

APC is utilized to realize active and reactive power

compensation in this project. As soon as a grid fault

occurs, the voltage and the frequency of the system

get disturbed, it will affect the stability of the power

system. However, the frequency and the voltage

magnitude can be compensated by active and reactive

power respectively. Hence, more and more APCs

have been developed with the function of active

power and reactive power compensation.

A ac–ac converter with bidirectional power flow

can be implemented by coupling the dc-link of a

PWM rectifier and a PWM inverter. The dc-link

quantity is then impressed by an energy storage

element that is common to both Stages: a capacitor

CDC for the voltage dc-link back-to-back converter

or an inductor LDC for the current dc-link back-to-

back converter. The PWM rectifier is controlled in

such a manner that a sinusoidal mains current is

drawn, which is in-phase or anti phase with the

corresponding mains line voltage. The

implementation of the V-BBC and C-BBC requires

12 transistors (typically IGBTs) and 12 diodes or 12

reverse conduction IGBTs (RC-IGBTs) for the V-

BBC and 12 reverse blocking IGBTs (RB-IGBTs) for

the C-BBC.

Due to the dc-link energy storage element, there is

an advantage that both converter stages are, to a large

extent, decoupled regarding their control for a typical

sizing of the energy storage. Furthermore, a constant

mains-independent input quantity exists for the PWM




inverter stage, which results in a high utilization of

the converter‟s power capability. On the other hand,

the dc-link energy storage element can have a

relatively large physical volume compared with the

total converter volume, and when electrolytic

capacitors are used for the dc-link of the V-BBC, the

service lifetime of the converter can potentially be

reduced.

II. PROPOSED SYSTEM

A. CIRCUIT DIAGRAM

The circuit diagram and control blocks of the

proposed three-phase back-to-back APC are shown in

Fig 1. It consists of two bidirectional ac-dc/dc-ac

converters. As soon as the voltage or frequency

disturbance on the weak micro-grid side is detected,

the converter connected to the weak grid will operate

as a dc-ac inverter and supply the demanded active

and reactive power from the dc-link to the disturbed

micro-grid. In the meantime, the active and reactive

power commands will be transferred to the active and

reactive current command, Id,cmd and Iq,cmd. The

Proportional-Integral (PI) controllers of the current

commands are designed in the conventional fashion.

Fig 1 Conceptual Diagram of Micro-grid

with back-to-back APC

Meanwhile, for power flow balancing, the

converter on the opposite side of the dc link will

operates as an ac-dc rectifier. For simple control, the

Direct-Quadrature Transformation method is used in

this paper. The three-phase voltages and the input

currents are converted into the directed axis voltage

and current components, Vd and Id, and the

quadrature axis voltage and current, Vq and Iq. Thus,

the complex power of the three-phase

rectifier/inverter can be written as:

𝑠 =3

2 𝑉𝑑𝐼𝑑 + 𝑉𝑞𝐼𝑞 + 𝑗 𝑉𝑞𝐼𝑑 − 𝑉𝑑𝐼𝑞 (1)

Fig 2 Circuit Diagram of back-to-back APC

The circuit diagram of back-to-back APC is shown

in the Fig 2. A phase-locked loop or phase lock loop

(PLL) generates an output signal whose phase is

related to the phase of an input signal. Here it is used

to fix the voltage value of q-axis as zero. Therefore,

the active and reactive power command can be:

𝑃𝑐𝑚𝑑 =3

2 𝑉𝑑𝐼𝑑 (2)

𝑄𝑐𝑚𝑑 = −3

2 𝑉𝑑𝐼𝑞 (3)

Fig 3 Conceptual Diagram of Droop Control

Strategy

As soon as the frequency or voltage disturbance of

the micro-grid occurs, the proposed APC should be

able to transfer appropriate active/reactive power to

the weak micro-grid. The droop control is commonly

adopted for power quality control because of its

simplicity. The conceptual diagrams of the droop

control strategy are shown in Fig. 3. The

https://en.wikipedia.org/wiki/Signal_(electrical_engineering)

https://en.wikipedia.org/wiki/Phase_(waves)




mathematical equations of the frequency and voltage

regulation via the active and reactive power

compensation can be expressed as:

𝑓𝑚𝑎𝑥 − 𝑓𝑚𝑖𝑛 = −2 × 𝑚𝑝 × 𝑃𝑚𝑎𝑥 (4)

𝑉𝑚𝑎𝑥 − 𝑉𝑚𝑖𝑛 = −2 × 𝑚𝑄 × 𝑄𝑚𝑎𝑥 (5)

where 𝑓𝑚𝑎𝑥 ,𝑓𝑚𝑖𝑛 ,𝑉𝑚𝑎𝑥and 𝑉𝑚𝑖𝑛 are the

maximum and minimum frequency and voltage of the

micro-grid, respectively. 𝑃𝑚𝑎𝑥 and 𝑄𝑚𝑎𝑥 represent

the maximum active and reactive of the APC. The

slope of f-P and V-Q droop characteristics are

represented as 𝑚𝑃 and 𝑚𝑄 respectively.

B. POWER CONDITIONER

A power conditioner (also known as a line

conditioner or power line conditioner) is a device

intended to improve the quality of the power that is

delivered to electrical load equipment. While there is

no official definition of a power conditioner, the term

most often refers to a device that acts in one or more

ways to deliver a voltage of the proper level and

characteristics to enable load equipment to function

properly. In some uses, power conditioner refers to a

voltage regulator with at least one other function to

improve power quality (e.g. power factor correction,

noise suppression, transient impulse protection,

etc.).The terms "power conditioning" and "power

conditioner" can be misleading, as the word "power"

here refers to the electricity generally rather than the

more technical electric power. Conditioners

specifically work to smooth the sinusoidal ac wave

form and maintain a constant voltage over varying

loads.

AC power, as delivered, is contaminated with

noise. Additional noise is added by your everyday

appliances, computer power supplies, etc. Without

exception, this degrades the performance of your

sensitive audio / video components. Also, electrical

surges and spikes have becomes common-place,

occurring on a daily basis. These and other harmful

AC events put valuable equipment at risk. A good

power conditioner filters and cleans incoming AC

power and dramatically improves your equipment's

performance. Audio sounds better and your picture

looks cleaner. It will increase the longevity of your

connected components since contaminated AC add

wear and tear to power supplies and other internal

circuits. A good power conditioner protects your

equipment from damaging AC events such as surges,

spikes, lightning and high voltage. An AC power

conditioner is the typical power conditioner that

provides "clean" AC power to sensitive electrical

equipment. Usually this is used for home or office

applications and has up to 10 or more receptacles or

outlets and commonly provides surge protection as

well as noise filtering.

Power line conditioners take in power and modify

it based on the requirements of the machinery to

which they are connected. Attributes to be

conditioned are measured with various devices, such

as, Phasor measurement units. Voltage spikes are

most common during electrical storms or

malfunctions in the main power lines. The surge

protector stops the flow of electricity from reaching a

machine by shutting off the power source.

The term "Power Conditioning" has been difficult

to define historically. However, with the advances in

power technology and recognition by IEEE, NEMA,

and other standards organizations, a new actual

engineering definition has now been developed and

accepted to provide an accurate depiction of this

definition. "Power Conditioning" is the ability to

filter the AC line signal provided by the power

company. "Power Regulation" is the ability to take a

signal from the local power company, turn it into a

DC signal that will run an oscillator, which generates

a single frequency sine wave, determined by the local

area needs, is fed to the input stage of power

amplifier, and is then output as specified as the ideal

voltage present at any standard wall outlet.

A micro-grid is different from a main grid system,

which can be considered as an unlimited power so

that load variations do not affect the stability of the

system. On the contrary, in a micro-grid, large and

sudden changes in the load may result in voltage

transient of large magnitudes in the AC bus.

Moreover, the proliferation of switching power

converters and nonlinear loads with large rated power

can increase the contamination level in voltage and

current waveforms in a micro-grid, forcing to

improve the compensation characteristics required to

satisfy more stringent harmonics standards. The APC

has proved to be an important alternative to

compensate current and voltage disturbances in

power distribution systems.

C. DESIGN OF POWER CONDITIONER

A good quality power conditioner is designed with

internal filter banks to isolate the individual power

outlets or receptacles on the power conditioner. This

eliminates interference or "cross-talk" between

components. If the application will be a home theater

system, the noise suppression rating listed in the

technical specifications of the power conditioner will




be very important. This rating is expressed in

decibels (db). The power conditioner will also have a

"joule" rating. A joule is a measurement of energy or

heat required to sustain one watt for one second,

known as a watt second. Since electrical surges are

momentary spikes, the joule rating indicates how

much electrical energy the suppressor can absorb at

once before becoming damaged itself.

D. USES OF POWER CONDITIONER

Power conditioners vary in function and size,

generally according to their use. Some power

conditioners provide minimal voltage regulation

while others protect against six or more power

quality problems. Units may be small enough to

mount on a printed circuit board or large enough to

protect an entire factory. Small power conditioners

are rated in volt-amperes (VA) while larger units are

rated in kilovolt-amperes (kVA). Ideally electric

power would be supplied as a sine wave with the

amplitude and frequency given by national standards

(in the case of mains) or system specifications (in the

case of a power feed not directly attached to the

mains) with an impedance of zero ohms at all

frequencies.

E. BACK-TO-BACK-CONVERTER

The main circuit of the back-to-back converter is

composed of renewable source, load, and switching

devices. The switching devices or IGBT are divided

into two sets that are equal to 24 pieces. The 12

switching devices will be operated as a rectifier, and

the 12 switching devices will be performed as an

inverter. It also has C1and C2, which is called DC-

link, between the rectifier and the inverter. Fig 4

represents the back-to-back converter.

Fig 4 Back-to-Back Converter

It consists simply of a force-commutated rectifier

and a force-commutated inverter connected with a

common dc-link. The properties of this combination

are well known; the line-side converter may be

operated to give sinusoidal line currents, for

sinusoidal currents, the dc-link voltage must be

higher than the peak main voltage, the dc-link voltage

is regulated by controlling the power flow to the ac

grid and, finally, the inverter operates on the boosted

dc-link, making it possible to increase the output

power of a connected machine over its rated power.

An important property of the back-to-back converter

is the possibility of fast control of the power flow. By

controlling the power flow to the grid, the dc-link

voltage can be held constant. The presence of a fast

control loop for the dc-link voltage makes it possible

to reduce the size of the dc-link capacitor, without

affecting inverter performance. In fact, the capacitor

can be made small enough to be implemented with

plastic film capacitors.

Fluctuations in the load cannot be smoothed in the

converter, but must be accommodated by other

means. One alternative is to simply transfer such

fluctuations to the power grid, but this may re-

introduce the line-current harmonics the back-to-back

converter is supposed to eliminate. However, load

fluctuations will be random and thus relatively

harmless compared to the in-phase harmonics

generated by diode rectifiers. Another alternative is

to use the load itself. In a typical drive, the

mechanical energy stored in the drive is several

orders of magnitude larger than the electrical energy

stored in the DC-link capacitor in a back-to-back

converter. If the application does not need servo-class

performance, there is no reason why the rotational

speed cannot be allowed to fluctuate slightly. A pump

drive, for instance, may be perfectly satisfactory if

the speed regulation performance is comparable with

a directly connected induction motor.

The smallest feasible capacitor, chosen on the

basis of switch-frequent voltage ripple, is too small to

absorb (within voltage limits) even the

[electromagnetic] energy stored in the main flux of a

connected electrical drive. This places high demands

on the controller which must be absolutely reliable. If

the controller fails, the stored energy may raise the

voltage of the DC-link beyond acceptable levels

(enough to break the rectifier and/or the inverter).

This may also result from circuit-breaker tripping. To

avoid DC-link overvoltage resulting from e.g

controller failure, also the back-to-back converter

must have a voltage limiting device. This can consist

of a traditional brake chopper. However, the average

power rating needed is much smaller than for a

conventional converter, although the peak power

rating would probably be more than the rated power

of the converter3. The chopper must be independent

of the converter controller to be operational in event




of a controller failure. Preferably, the chopper should

operate directly from the DC-link voltage.

F. OPTIMAl CURRENT REGULATION

STRATEGY

The conceptual diagram of the dc-link voltage and

ac-line current regulation strategy is shown in Fig 5.

At first, the reference voltage Vdc,high and Vdc,low

should be determined. If the dc-link voltage is greater

than the high voltage bound, Vdc,high, the output

current command, Id,ref, should be decreased with a

constant value, ΔId. If the dc-link voltage is lower

than the low voltage bound, Vdc,low, the output

current command, Id,ref, should be increased with a

constant value, ΔId. Otherwise, the current reference

should remain unchanged. The output current

command, Id,ref, will be changed at the beginning of

the ac mains cycle with the help of using PLL

It can be expressed as the following equations:

If 𝑉𝑑𝑐 (𝑛) > 𝑉𝑑𝑐 ,𝑕𝑖𝑔𝑕 ,

then 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛) = 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛−1) − ∆𝐼𝑑 (6)

Else if 𝑉𝑑𝑐 (𝑛) < 𝑉𝑑𝑐 ,𝑙𝑜𝑤 ,

then 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛) = 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛−1) + ∆𝐼𝑑 (7)

Otherwise, 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛) = 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛−1) (8)

Fig 5 Conceptual diagram of current regulation

strategy

It is very simple method of control but selecting a

proper current command is difficult for different

power levels. If we select a small ΔId value, the

response of dc link regulation will be slow. If we

select a large ΔId value, it will increase the regulation

response but the large ac current variation will bring

a negative impact to the power quality. The optimal

ac line current regulation strategy integrated with the

voltage trend method is proposed in this paper to

reduce the change of input current and to achieve dc

link regulation,

To avoid rapid dc-link voltage change, the current

change command should be as small. Eventually, the

optimal ac line current adjustment value, ΔId,opt, for

the high/low dc-link voltage bound can be expressed

as:

∆𝐼𝑑 ,𝑜𝑝𝑡 −𝐻 =𝐶𝑑𝑐

3×𝑇𝑎𝑐 ×𝑉𝑑[𝑉𝑑𝑐 ,𝑕𝑖𝑔𝑕

2 − 2𝑉𝑑𝑐 (𝑛)2 + 𝑉𝑑𝑐 (𝑛−1)

2 ]

(12) (9)

∆𝐼𝑑 ,𝑜𝑝𝑡 −𝐿 =𝐶𝑑𝑐

3×𝑇𝑎𝑐 ×𝑉𝑑[𝑉𝑑𝑐 ,𝑙𝑜𝑤

2 − 2𝑉𝑑𝑐 (𝑛)2 + 𝑉𝑑𝑐 (𝑛−1)

2 ]

(13) (10)

The optimal current regulation strategy can be

expressed as:

If 𝑉𝑑𝑐 (𝑛) > 𝑉𝑑𝑐 ,𝑕𝑖𝑔𝑕 and ∆𝑉𝑑𝑐 (𝑛−1) > 0,

then 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛) = 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛−1) − ∆𝐼𝑑 ,𝑜𝑝𝑡 −𝐻 (11)

Else if 𝑉𝑑𝑐 (𝑛) < 𝑉𝑑𝑐 ,𝑙𝑜𝑤 and ∆𝑉𝑑𝑐 (𝑛−1) < 0

then 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛) = 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛−1) + ∆𝐼𝑑 ,𝑜𝑝𝑡 −𝐿 (12)

Otherwise, 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛) = 𝐼𝑑 ,𝑟𝑒𝑓 (𝑛−1) (13)

G. SIMULATION OF PROPOSED SYSTEM

Fig 6 simulink model of proposed system

The simulink model of the proposed system is

shown in the Fig 6. It represents the back-to-back

converter connected between two microgrids.




H. PHASE LOCKED LOOP

A phase-locked loop (PLL) is an electronic circuit

with a voltage- or current-driven oscillator that is

constantly adjusted to match in phase (and thus lock

on) the frequency of an input signal. In addition to

stabilizing a particular communications channel

(keeping it set to a particular frequency), a PLL can

be used to generate a signal, modulate or demodulate

a signal, reconstitute a signal with less noise, or

multiply or divide a frequency. PLLs are frequently

used in wireless communication, particularly where

signals are carried using frequency modulation (FM)

or phase modulation (PM). PLLs can also be used in

amplitude modulation (AM). PLLs are more

commonly used for digital data transmission, but can

also be designed for analog information. Phase-

locked loop devices are more commonly

manufactured as integrated circuits (ICs) although

discrete circuits are used for microwave.

A PLL consists of a voltage-controlled oscillator

(VCO) that is tuned using a special semiconductor

diode called a varactor. The VCO is initially tuned to

a frequency close to the desired receiving or

transmitting frequency. A circuit called a phase

comparator causes the VCO to seek and lock onto the

desired frequency, based on the output of a crystal-

controlled reference oscillator. This works by means

of a feedback scheme. If the VCO frequency departs

from the selected crystal reference frequency, the

phase comparator produces an error voltage that is

applied to the varactor, bringing the VCO back to the

reference frequency. The PLL, VCO, reference

oscillator, and phase comparator together comprise a

frequency synthesizer. Wireless equipment that uses

this type of frequency control is said to be frequency-

synthesized.

Since a PLL requires a certain amount of time to

lock on the frequency of an incoming signal, the

intelligence on the signal (voice, video, or data)

can be obtained directly from the waveform of the

measured error voltage, which will reflect exactly the

modulated information on the signal.

Fig 7 Block Diagram of PLL

The block diagram of PLL is shown in the Fig 7. A

phase detector compares two input signals and

produces an error signal which is proportional to their

phase difference. The error signal is then low-pass

filtered and used to drive a VCO which creates an

output phase. The output is fed through an optional

divider back to the input of the system, producing a

negative feedback loop. If the output phase drifts, the

error signal will increase, driving the VCO phase in

the opposite direction so as to reduce the error. Thus

the output phase is locked to the phase at the other

input. This input is called the reference.

I. PI CONTROLLER

PI controller will eliminate forced oscillations and

steady state error resulting in operation of on-off

controller and P controller respectively. However,

introducing integral mode has a negative effect on

speed of the response and overall stability of the

system. Thus, PI controller will not increase the

speed of response. It can be expected since PI

controller does not have means to predict what will

happen with the error in near future. This problem

can be solved by introducing derivative mode which

has ability to predict what will happen with the error

in near future and thus to decrease a reaction time of

the controller. PI controllers are very often used in

industry, especially when speed of the response is not

an issue.

J. SIMULATION RESULTS

Fig 8 Input current of back-to-back APC

The input current of back-to-back active power

conditioner is shown in the Fig 8. The input current

variation with the proposed strategy is relatively

smaller without bringing negative impact of power

quality of ac mains.

Fig 9 output current of back-to-back APC




The output current of back-to-back active power

conditioner is shown in the Fig 9. Here the x axis

denotes the time and the y axis denotes the current

value.

Fig 10 Input voltage of back-to-back APC

The input voltage of back-to-back active power

conditioner is shown in the Fig 10. Depending upon

the grid voltage, the reactive power is injected or

absorbed.

Fig 11 Output voltage of back-to-back APC

The output voltage of back-to-back active power

conditioner is shown in the Fig 11. The output

voltage is lesser than the input voltage. The output is

fed to the weak grid.

Fig 12 DC link voltage of back-to-back APC

The DC link voltage of back-to-back active power

conditioner is shown in the Fig 12. This figure shows

the charging and discharging of capacitor. By using

proposed strategy the voltage reaches the hysteresis

band is minimum.

In order to remain the power flow balance, the dc-

link voltage is regulated between the hysteresis

bound by the input current, of the front-end

converter. As soon as the high voltage bound is

detected, the input current reference, Id,ref, will be

reduced. Similarly, if the low voltage bound is

detected, the input current will be increased.

Fig 13 Input power of back-to-back APC

The input power of back-to-back active power

conditioner is shown in the Fig 13. Here the x axis

represents time and the y axis represents power

values. Depending upon the frequency APC will

inject or absorb the active power.

Fig 14 PWM generation

The pwm generation for the converters is shown in

the Fig 14. The generated pulses are given to the

switches in the converter. Here we use 6 switch

converters.

III CONCLUSION

This paper presents a three-phase back-to-back

APC with optimal current regulation strategy for

micro-grid applications. To achieve high stability, the

frequency and the voltage of the microgrid is

controlled by using bidirectional power flow control.

The demanded active and reactive power of the APC

via bi-directional power flow control provides the

ability to improve the power quality and stability of

micro grids. Optimal current regulation method for

the APC is proposed in this paper. . When fault on one microgrid is detected, the other microgrid can

provide active and reactive power compensation via

the APC. Hence, the APC becomes a necessary

component for the micro-grid application Under

steady-state, the optimal ac line current regulation

method is able to regulate the dc-link voltage and the




injected ac line current variation will be minimized.

By using the optimal current regulation strategies, the

required dc-link capacitance of the back-to-back APC

can be reduced.

ACKNOWLEDGMENT

First of all we would like to thank the almighty for

giving me sound health throughout my paper work. This

research was supported/partially supported by our college.

We thank our staffs from our department who provided

insight and expertise that greatly assisted the research,

although they may not agree with all of the

interpretations/conclusions of this paper.

REFERENCE

[1] H. Akagi and R. Kitada, “Control and design of a

modular multilevel cascade BTB system using bidirectional

isolated dc/dc converters,” IEEE Trans. Power Electron,

vol. 26, no. 9, pp. 2457-2464, 2011.

[2] Y. -T. Chen, Y. –F. Chen, C. –Y. Tang, Y. –M. Chen

and Y. –R. Chang, "An active power conditioner with a

multi-mode power control strategy for a microgrid," in

Proc. IEEE IFEEC, pp.93-97, 2013.

[3] Y. M. Chen, H. C. Wu, M. W. Chou, and K. Y. Lee,

“Online failure prediction of the electrolytic capacitor for

LC filter of switching-mode power converters,” IEEE

Trans. Ind. Electron., vol. 55, no. 1, pp. 400– 406, 2008.

[4] Y. M. Chen, H. C. Wu, Y. C. Chen, K. Y. Lee, and S. S.

Shyu, “The ac line current regulation strategy for the grid-

connected PV system,” IEEE Trans. Power Electron, vol.

25, no. 1, pp. 209-218, 2010.

[5] Y. M. Chen, C. S. Cheng, and H. C. Wu, “Grid-

connected hybrid PV/wind power generation system with

improved DC link voltage regulation strategy,” in Proc.

IEEE APEC, pp. 1088–1094, 2006.

[6] B. G. Gu and K. Nam, “A dc-link capacitor

minimization method through direct capacitor current

control,” IEEE Trans. Industry Applications, vol. 41, no. 5,

pp. 573-581, 2005.

[7] M. L. Gasperi, "Life prediction model for aluminum

electrolytic capacitors," in Proc. IEEE IAS, pp. 1347–

1351,1996.

[8] M. Hagiwara and H. Akagi, “An Approach to regulating

the dc-link voltage of a voltage-source BTB system during

power line faults, ” IEEE Trans. Industry Applications, vol.

42, no. 2, pp. 1263-1271, 2005.

[9] I. Jlassi, J. O. Estima, S. K. El Khil, N. M. Bellaaj and

A. J. Marques Cardoso, "Multiple Open-Circuit Faults

Diagnosis in Back-to-Back Converters of PMSG Drives for

Wind Turbine Systems," IEEE Trans. Power. Electron.,

vol. 30, no. 5, pp. 2689-2702, 2015.

[10] R. P. Kandula, A. Iyer, R. Moghe, J. E. Hernandez and

D. Divan, "Power Router for Meshed Systems Based on a

Fractionally Rated Back-to-Back Converter," IEEE Trans.

Power. Electron., vol. 29, no. 10, pp. 5172-5180, 2014.

OPTIMAL CURRENT REGULATION STRATEGY FOR THREE-PHASE BACK-TOBACK ACTIVE POWER CONDITIONERS

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