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Margo Pujiantara et. al. / International Journal of Engineering Science and Technology Vol. 2(8), 2010, 3909-3917

ISSN: 0975-5462 3909

DVR CONTROL USING FUZZY POLAR

FOR VOLTAGE SAGS RESTORATION

ON 4-WIRE SYSTEM

MARGO PUJIANTARA

Electrical Engineering, Institute Technology of Sepuluh Nopember, Jl. Raya ITS, Surabaya, 60111, Indonesia

[email protected]

RIO INDRALAKSONO, SEPTIAN DWIRATHA, M. ASHARI, MAURIDHI HERY PURNOMO

Electrical Engineering, Institute Technology of Sepuluh Nopember, Jl. Raya ITS, Surabaya, 60111, Indonesia [email protected]

TAKASHI HIYAMA

Electric Power System Laboratory, Kumamoto University, Kumamoto, 860-8555, Japan

[email protected]

Abstract :

Voltage sags is destructive interference voltage profile and most often occur in the industry. Consequences which can be caused by such interference is black out, the failure of function, even damage to sensitive equipment. There are several methods that can solve the voltage profile problem. One method that is considered the most effective and efficient to maintain the voltage profile according to previous research is the method of the Custom Power Supply (CUPS) in the form of Dynamic Voltage Restorer (DVR). In this research, selected Polar Fuzzy control method for controlling the DVR because it has proved better than other methods according to previous research and is able to restore the voltage profile without prejudice and without the use of zero sequence blocking transformers. From the simulation results found that DVR Polar Fuzzy control method is able to restore the voltage profile due to voltage sags at an average of 99.83%.

Keywords: DVR, Fuzzy Polar, Voltage Sags.

1. Introduction

An electrical power distribution system which is ideal to give customers the power flow is not interrupted by

an unlimited power rating and having a pure sinusoidal wave at the frequency and magnitude that have been determined. In fact, a power system has several features that are not ideal, and then have the impact on power quality. Voltage sags is one of power quality problems. Prevent all kind voltage sags is not possible, but handling stress sags should be done. Voltage sags is a serious problem that can damage sensitive equipment ex, motor drives, computers, programmable logic controller (Nguyen, 2004).

According to ANSI std. 1100-1992, are included in the category of voltage sags is 0.1 pu voltage drop to 0.9 pu within 0.5 cycle to 1 minute. Based on European standard EN 50160-2000, "Voltage Characteristics of electricity supplied by public distribution systems" (Cenelec, 1999) blinking voltage is defined as a sudden decrease in voltage from 90% to 10% of nominal voltage, followed by recovery at a certain period. Period was 10 ms to 1 minute. Voltage sags is defined by the IEEE std. 1159-1995 as a decrease in voltage Root Mean Square (RMS) between 0.1 and 0.9 Per Unit (PU) for a period of between half a cycle and less than one minute. In other words, if the voltage falls below 90% of the nominal and less than one minute, this is known as voltage fluctuations blink.

Fuzzy polar first introduced by Takashi Hiyama in 1991 (Hiyama et. Al., 1991). Fuzzy Polar is a decision that the optimal method of mapping the signal in polar areas. These parameters are controlled by Fuzzy Polar on polar fields.. Each position in the polar areas represents major control signals required. The main principle of the


ISSN: 0975-5462 3910

DVR

Main Bus

Sensitive load Bus

Normal load Bus

Grounding

Ground faultMain Bus

Normal load Bus

Grounding

Ground fault

DVR

Sensitive load BusBlocking Transformer

fuzzy polar shift which determines the magnitude of the input signal to be controlled to the equilibrium conditions (desired conditions).

Signal to be controlled is represented in two polar parameters of magnitude and angle. In the basic application, the function of the fuzzy polar controller is used to replace the function of the PI (Hiyama et. Al., 1993). Control signal given by the fuzzy polar to be robust so that the input signal provides a more optimal results.

DVRs in general on the three wire method using blocking transformer with the assumption that the fault is a three phase ground fault. When an interruption occurs, the components of one phase ground zero with a role big enough so that the resulting lack of a good recovery (Chung et. Al., 2001). using four-wire, zero sequence is controlled zero so that the resulting good restore voltage.

This paper aims to create a DVR-based fuzzy polar controller for improving voltage sag in the system 3 phase 4 wire using the VSI. So we get better results and recovery voltage during voltage sags can be achieved without the shift in nominal voltage phase angle and harmonics can be well damped.

2. System Modeling

Typically basic configuration DVR consists of Booster Transformer, Voltage Source Inverter, System Control, Energy Storage which consists of the source DC and Blocking Transformer. When an interruption occurs, the voltage at the sensitive load bus has decreased. Booster transformer inject voltage transformer will provide in accordance with the decrease in voltage at load bus voltage at load bus so sensitive to be constant. Booster Transformer get the injection voltage source from the Voltage Source Inverter (VSI) which is controlled by the Voltage Regulator. The amount of voltage injection given by Voltage Source Inverter (VSI) was formulated as follows:

Ul= Us+ Uinj (2.1)

where, Ul = voltage sensitive load Us = voltage sags Uinj = voltage injection

Installation DVR on a simple distribution system model is shown in Figure 1a and 1b. Figure 2.1a represents the installation of a conventional DVR system that still uses the blocking transformer, while Figure 2.1b represent the installation of the proposed DVR without blocking transformers.

(a) (b)

Figure 2.1a. Distribution system model with the installation of a typically DVR. 2.11b. Distribution system model with the installation of the proposed DVR.

When the voltage sags into a voltage asymmetry is restored to normal voltage symmetry. At normal voltage conditions, the power load on each phase can be written as follows.

Sl=Ul.Il*=Pl+jQl (2.2) where, Il = load current Pl = active power Ql = reactive power

To obtain the recovery voltage is required injection power from the DVR so that the power flow of each phase is shown in equation (2.3).


ISSN: 0975-5462 3911

Sl=(Pl+jQ)l=(P+jQ)s+(P+jQ)inj (2.3) where,

(P+jQ)s represents sags quantity (P+jQ)inj represents DVR injection quantity

Blocking Transformer on conventional DVR is used to prevent voltage / zero sequence currents that occurred at the time of disturbance on the bus or other feeder that led to sensitive load. Blocking Transformer which installed on system with winding configuration Y- caused zero sequence impedance infinite. However Blocking Transformer cant operate on 3 phase 4 wire system. So we need a controller that can control the zero sequence components when single phase to ground fault occurs.

In the distribution system with neutral point grounding, most faults are single phase to ground disturbance. Single phase to ground fault on the normal load feeder will result in voltage sags on the feeder sensitive load. Phasor diagram when there is a single phase to ground disturbance is shown in Figure 2.2 Condition of voltage at the sensitive load prior to fault can be described in equation (2.4, 2.5, 2.6).

(0) (1) (2) a a a aV V V V (2.4) (0) (1) (2) b b b bV V V V (2.5)

(0) (1) (2) c c c cV V V V (2.6)

Figure 2.2. Phasor voltage of three phases during a phase to fault ground During the disturbances, the voltage equation can be written into,

cos sin

1 13

2 21 1

32 2

a

b

b

V V jV

V j

V j

(2.6)

where, V = magnitude sags voltage = phase angle jump

Zero sequence components during fault can be explained in the following:

0

1( )

3a cbV V V V

cos sinaV V jV (2.7)

From equation (2.5) shows that zero sequence components was not equal to 0. This shows that the zero sequence components must be compensation. Compensation method d, q and 0 for voltage regulator control DVR using Fuzzy Polar, modeled in Figure 2.3 and full scheme for proposed DVR shown in Figure 2.4.

Va

Vc

Vc

V


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Vabc

Vabc

to

dq0

V0 ref+

-

Vd ref+

Vq ref

d

dt

d

dt

d

dt

Fuzzy

Polar

rule base

V0

Vd

Vq

Vd

Vq

V0

dq0

to

abc

Vd

Vq

V0

PWM

-

Figure 2.3. DVR voltage regulator control model using Fuzzy Polar

Figure 2.4. Full scheme of proposed DVR using Fuzzy Polar controlled method.

3. Fuzzy Polar

Fuzzy polar first introduced by Takashi Hiyama in 1991 (Hiyama et. Al., 1991). Fuzzy Polar is a decision that the optimal method of mapping the signal in polar areas. These parameters are controlled on Fuzzy Polar polar fields such as represented in Figure 3.1. Each position in the polar areas represent major control signals required. The main principle of the fuzzy polar shift which determines the magnitude of the input signal to be controlled to the equilibrium conditions (desired conditions).

Signal to be controlled is represented in two polar parameters of magnitude and angle. In the basic application, the function of the fuzzy polar controller is used to replace the function of the PI (Pujiantara et. Al., 2007, 2008, 2009). Control signals generated by the fuzzy polar referring to the input signal is robust, thus providing a more optimal results.

On fuzzy polar, there are only two membership functions. Determination of the control signal becomes faster and easier (Pujiantara et. Al., 2010). Another advantage of the fuzzy polar is the polar fuzzy expert system does not need to determine the fuzzy rule base on different systems.


ISSN: 0975-5462 3913

Figure 3.1. Polar Form on Polar Fuzzy system

On Fuzzy polar, the desired output signal at t is represented as a point O. The signals will be controlled at the

time t is described as a point in the field of polar coordinates p(k) = [D(k), (k)]. The magnitude p(k) represents the size of the input signal will be shifted / repaired to the desired signal and is represented by point O or equilibrium point. The value of p(k) can be obtained by representing the axis Zs and ZaAs as components that affect the signal to be controlled (Hiyama et. Al, 1993) or change the signal to be controlled at t into components [Zs, ZaAs] as illustrated in Figure 3.2.

Figure 3.2. Controller Diagram of Fuzzy Polar

As is a derivative multiplier parameter that represents a large degree of sensitivity of the resulting control

signal. Mathematically, the parameters of the Fuzzy Polar can be obtained by the following equation: p(k)=[Zs(k), AsZa(k)] (3.1) D(k)=(Zs(k)2+AsZa(k)2) (3.2) (k)=tan-1(AsZa(k)/ Zs(k)) (3.3)

where,

p(k) = input in the polar axis Zs(k) = Horizontal input in the polar axis AsZa(k) = Vertical input in the polar axis D(k) = Magnitude of input in the polar axis (k) = Angle input in the polar axis

In Figure 3.1., Sector "A" represents the output control signals which are positive and the B sector output control is represent negative signal. Determination of the control signal magnitude is influenced two parameters: D(k) and (k) and so we need two rule base. Put simply, this rule base can be represented in the membership function as depicted in Figure 3.3.


ISSN: 0975-5462 3914

1

0 360 315 270 180 135 90 0

= 90 N( ) ) P(

grade

[ degree ]

1

grade

0 Dr Amplitude D(k)

G(D(k))

Figure 3.3. Membership Function Angle and Amplitude Fuzzy Polar

Defuzzyfication in fuzzy polar can be explained by mathematical equations such as (3.4)

U(k)= G(D(k)).[N((k))-P((k))].Umax (3.4) where, U(k) = Value of fuzzy control polar

G(D(k)) = Value of membership function amplitude N((k)) = Value of the first membership function of the angle P((k)) = Membership value of the second function of the angle Umax = Maximum value of the control signal

With Umax is a constraint, which limits the maximum allowed control signal to fix the input signal.

4. Simulation

On Fuzzy Polar method required the determination of some parameters, Umax and As. Umax value can be known using equation (4.1). To get the value of Umax, given the disruption of distribution systems with three phase impedance large enough so that the voltage sags 0% occur. Voltage sags 0% means that the voltage distribution lines in the event of disruption is Vrms = 0 Volt and requires an injection to recover the value of this condition. Large value when the condition of injections given 0% voltage sags is the largest injection when an interruption occurs and represents the maximum control value for the injection.

Umax= 1 / ( G(D(k)).[N((k))-P((k))] ) (4.1)

Figure 4.1. System power distribution with voltage sags 0%

To get the value of Umax, it is simulated by giving a three phase short circuit that resulted in voltage sags 0% as depicted in Figure 4.1. Simulation is done by time sampling = 10-6, during the 0.02 seconds and the interruption given at 0.001 to 0.01 seconds. To obtain the required parameters, the data taken at 0.00785 seconds and was chosen As = 0:19.


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Figure 4.2. Error signal in system power distribution with 3 phase short circuit disturbance on coordinate dq0

Based on the simulation results are shown in Figure 4.2. It is known that a large error signal from comparison with the reference signal sensing during the disturbance, the axis d = 1, q = 0 axis and the axis 0 = 0. With this situation, it is known that the maximum required control signal = 1 pu at d-axis to recover the maximum voltage sags or 0%. From simulation, shown that the error signal on each axis in the coordinate dq0 that have changed the parameters into two polar areas Za and Zs, can be seen that the result of changes in polar areas indicates that the error signal appears only in the field of polar axis-d and another axis didnt have any magnitude same as before converted in polar form. Signals from the three axis d, q and 0 will be input into the fuzzy rule base separately to obtain the required control signals.

Simulation result that shown on Table 4.1., obtained the results of the output of the fuzzy rule base in polar form, Parameters in the d-axis component can be used to obtain the value of Umax-d because signal control only appear in d-axis for full restoration on voltage sagas 0%. Using equation (4.1), obtained Umax = 4,18

Table 4.1. d-axis parameters

Parameters Value

G(D(k)d) 1 N((k)d) 0,6196 P((k)d) 0,3804

The simulation is repeated again by giving a phase asymmetry of ground disturbance and the result is

shown in Figure 4.3. From the pictures can be seen that the amplitude of the d-axis control signal, q, and 0 is the same. Thus we can conclude that the value of Umax for the third axis is the same.

Figure 4.3. Signal control of voltage restorer with 1 phasa short circuit to ground disturbance


ISSN: 0975-5462 3916

5. Result and Conclusion

In this study, the power line distribution are given short circuit 3 phase, 2 phase, 2 phase ground, and the 1 phase ground. Given large disturbance varied causing voltage sags 30%, 50% and 70%. Figure 5.1 to 5.4 shows recovery performance by the control voltage regulator for the recovery of voltage sags 50% in various disturbances. From the simulation results as shown in Table 5.1 can be seen that the recovery voltage sags using a voltage regulator control Fuzzy Polar method is able to recover voltages profile up to 100%, average recovery is 99.83% and the lowest error is 0.17% for overall recovery.

Table 5.1. Restoration performance using proposed DVR

Study Case Voltage

Sags

3F 2F 2FG 1FG

70% 50% 30% 70% 50% 30% 70% 50% 30% 70% 50% 30%

Restoration 100% 100% 100% 100% 99% 100% 100% 100% 100% 99% 100% 100%

Figure 5.1. Voltage sags 50% restoration for 1 phase to ground short circuit disturbance using voltage regulator with Fuzzy Polar control method in pu

Figure 5.2. Voltage sags 50% restoration for 2 phase short circuit disturbance using voltage regulator with Fuzzy Polar control method in pu


ISSN: 0975-5462 3917

Figure 5.3. Voltage sags 50% restoration for 2 phase to ground short circuit disturbance using voltage regulator with Fuzzy Polar control method in pu

Figure 5.4. Voltage sags 50% restoration for 3 phase short circuit disturbance using voltage regulator with Fuzzy Polar control method in pu References

[1] Il-Yop Chung, Sang-Young Park, Seung-Il Moon, Seong-Il Hur, The control and analysis of zero sequence components in DVR system, Power Engineering Society Winter Meeting, 2001. IEEE

[2] P.T. Nguyen and Tapan. K. Saha, Dynamic Voltage Retorer Againts Balanced and Unbalanced Voltage Sags : Modelling and Simulation, IEEE 2004.

[3] Pujiantara, M., Mauridhi Hery P, Mochamad Ashari, DVR modeling based on fuzzy polar controller to restore balanced and unbalanced sag voltage, SITIA, Surabaya, Mei 2007.

[4] Pujiantara, M., Mauridhi Hery P, Mochamad Ashari, Hendrik, T Hiyama, Balanced Voltage Sag Correction using Dynamic Voltage Restorer Based on Fuzzy Polar Controller, ICICIC conference, Kumamoto Japan, 5-7 September 2007.

[5] Pujiantara, M., M Hery-Purnomo, M Ashari, Zaenal PA, T Hiyama (2008), Compensation of Balanced and Unbalanced Voltage Sags using Dynamic Voltage Restorer Based on Fuzzy Polar Controller, International Journal of Applied Engineering Research (IJAER) - RESEARCH INDIA PUBLICATIONS, IJAER 455 Vol.3 No.7, Delhi India.

[6] Pujiantara, M., Mauridhi Hery P, Mochamad Ashari, Zaenal PA, T Hiyama, Dynamic Voltage Restorer Based on Fuzzy Polar as Voltage Sag Restorer and Voltage Distortion Compensator, ICA conference, Bandung, 2009.

[7] Pujiantara, M., M Hery-Purnomo, M Ashari, Zaenal PA, T Hiyama (2008), Advanced DVR with Zero-Sequence Voltage Component And Voltage Harmonic Elimination for Three-Phase Three-Wire Distribution Systems, IPTEK, The Journal for Technology and Science, Vol. 20, No. 4, November 2009.

[8] T. Hiyama, Real Time Control of Micro-Machine System Using Microcomputer-Based Fuzzy Logic Power System Stabilizer, Presented at the 1993 Summer Power Meeting, paper no. 93 WM 128-9 EC.

[9] T. Hiyama, Robustness of Fuzzy Logic Power System Stabilizers Applied to Multimachine Power Systems, Presented at the 1993 Summer Power Meeting, paper no. 93 SM 551-2 EC.

[10] T. Hiyama and T. Sameshima, Fuzzy logic Control Scheme for On-line Stabilization of Multimachine Power System, Fuzzy Sets and System, Vol. 39, No. 2 (1991) pp. 181-194.

[11] EN 50160. Voltage characteristics of electricity supplied by public distribution systems. Cenelec, Brussels, Belgium, November 1999.

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