Low Cost Voltage Regulator for Micro Scale HydroElectricity Generators

W. Rameesha De Silva, Rohan Munasingha,Amith MunindradasaElectronics and Telecomunication Engineering Dept.

University of MoratuwaSriLanka

ramee,rohan,amith ent.mrt.ac.lkrameesha24@yahoo.com

Abstract- This paper presents design and development of alow cost voltage regulator for Micro scale hydro electricitygenerators operated in rural areas where national grid electricityis not available. Most of the rural villages in heavily depend onmicro scale hydro electricity generators for electricity because oflow cost and availability. One of the major problems they have islack of controllability of the power and voltage of thesegenerators. Most of them use simple voltage regulators base onfixed dummy loads with can be selected under the house loadingconditions. These regulators are very inefficient and most of thetime they cannot supply enough voltage levels or power tooperate high power house hold appliances. As solution to this wehave developed a PIC micro-controller based voltage regulatorthat can dynamically adjust the power supplied to the house andcan supply maximum power when required. Remaining power iseffectively used for water heating proposes. We have tested thistechnique with a 2KW synchronize induction generatorsupplying power to a medium size house ,under various loadingand unloading conditions of the house hold appliances like TV,Iron, and washing machine, and we have obtained satisfactoryresults.

I. INTRODUCTION

Most of the third world countries suffer from the powercrisis and rural areas of these countries are not supported by themain power grid. This is because in rural areas humanpopulation density is low and extension of power grid is noteconomical for the major electricity suppliers and governments.As a result most of the rural villages are suffer from the lowliving conditions due to lack of electricity. For a solution mostgovernments and NGOs are encourage the people in these ruralareas to go for local power generation techniques. For examplesolar, wind, micro scale water electricity generation, woodthermal (Dendro) electricity generations can be mentioned.

Even though most of these techniques are work, theycannot use the full potential of the energy source due toprimitive nature of the generation and controlling techniques.

And also they cannot go for the sophisticated designsbecause of the economy and the scale of these systems.

Here we have address one of the problems related tomicro scale water electricity generation. One of the majorproblems in the micro scale water electricity generators iscontrolling of the power it generates. In lager systems this iscontrolling by changing the nozzle orifice or using a waterdamper. But in small systems this is more expensive and notpractically used. In small systems fixed dummy load orselectable type dummy load is used. In these systems energydissipated through the dummy load is wasted and usually usersare suffering from lack of voltage to operate their appliancesand some times they have to repeatedly change the load settingaccording to the power requirements.

In this system design we have proposed a controller todynamically and efficiently adjust power dissipation throughthe dummy load. This technique will supply full power to thehouse when required and also limit the voltage level at pre-settable level under low load conditions.

And also system offer one major advantage. As the housevoltage level can be set by the controller, user has some controlto vary the amount of power dissipation through the dummyload. This is very useful when dummy load energy is used for auseful work like water heating. In our design implementation,dummy load was a water heater and user can get more hotwater by simply selecting low voltage reference value for thehouse voltage.

Controller was tested with a 2KW synchronize inductiongenerator supplying power to a medium size house and it gavegood results under various loading and unloading conditions ofthe house hold appliances like TV ,Iron, washing Machine etc.

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II. OVERALL MICRO HYDRO SYSTEM (j + 1 )

Figl. System block diagram

Where; Vh is the line voltage, Vref is the desired line voltage,y is the triac firing angle, and fc is the generator frequency.

As shown in Figure 1 house load and the water heaterconnected in parallel with the Induction generator. Accordingto this configuration same voltage presents between theinduction generator terminals, house load and the water heater.Here voltage regulation is done by adjusting the load visible tothe generator by controlling the power dissipated through thewater heater. As visible load increase generator gets more loadand voltage drops and vise versa. Power to the water heater iscontrolled by a Triac where is firing angle is controlled using a

PIC based controller. Controller decide suitable firing angle (y)by considering set voltage (Vref), house voltage(Vh), generator frequency (fQ) and present firing angle.

A. Controller design

Here controller increment or decrement AP amount to thecurrent dissipated power to adjust the dummy load power. APis a constant value and can be set at the controller initialization.

AP = f (y)

P is a nonlinear function of y (Triac firing angle).

P= V2 /R

P (Vmax /R) sin 2(ct) d (cot)0

P Pmax0

sin 2(cot) d (cot)

Firing angle vs Power

0k

100

90

80

70

60

50

40

30

20

10

0

- Power

1 11 21 31 41 51 61 71 81 91 101111121131141151161171181

Firing angle

Fig3. Graph for diverted power percentage againstfiring angle

Controller is a simple close loop controller with a voltagefeedback.

Vref

Vh fc

As shown in Figure 3 relation between firing angle andpower is not linear. To keep the AP constant we used a look uptable that gives Firing angle against the Power o.

A graph based on the Firing angle (0) vs P is shown on

Figure 4.

Here we have limited the firing angle to be less than 170 °.This will still gives the 99.90 power output and avoid theproblem of miss firing that could happened in the next cycledue to frequency variations of the turbine.

Fig 2. Controller block diagram

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P (i) + A P

z

Firing angle vs power%Firing angle

180

160

140 -

120

x 100 -

S 80 -

60-

40 -

20

0-1 11 21 31 41 51 61 71 81 91

Power %

Fig4. Graph for firing angle against powerpercentage

Fig5. Pictures of the voltage controller and theinduction generator

B. Controller block diagram

Fig6. Detail controller block diagram

Detail controller block diagram is shown in Figure 6.Controller has two micro-controllers, one work as a master(PIC 16F877A) and other work as Slave (PIC 16F876A).Master processor handles the calculation part of the triactiming (y) and also handles three parallel processes which arefrequency monitoring, display driving and voltagemeasuring. Calculated firing angle is then transmitted to the

slave through an 8bit data bus. Master and slave aresynchronized with the zero crossing pulse generated by thezero crossing detecting.circuit. Slave is dedicatedly reservedfor monitoring the zero crossing and firing the traic toachieved accurate timing. Controller also has a protectioncircuit to protect the house appliances from high voltages. Itwill cut off the house power supply through a relay when theline voltage goes over the High voltage threshold limit.

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III. RESULTS AND DISCUSSION

This design was tested under the operation of varioushousehold equipments. Our main concern was to study thebehavior of the voltage fluctuations under heavy loadvariations. We tested electric iron, Television, Washingmachine which absorbs heavy current at the starting or on theoperation. And combine operations of these equipments werealso tested.

Hi voltage threshold limit was 240V and low voltagethreshold was 150 V. Our primary intentions were to keepthe line voltage between these voltage limits which preventsthe controller from shutting down the house power and alsoto be stable.

To achieve this two controller parameters AP andSampling Time (Ts) was adjusted. And Voltage fluctuationswere monitored and plotted using a real time plottingsoftware. Several experiments were done by changing APand Ts values. Increase of AP decrease the voltageovershoots caused by heavy load switching but also degrades

the system stability. Increment of the Ts caused the sluggishresponse the voltage transient and decrement of Ts makesystem unstable.

After few experiments suitable values for AP and Ts wereable to found. AP = 3°, Ts = 60ms were the suitable valuesfor the controller to be stable under the specified loadconditions.

Figures [7-9] shows the variation of line voltage, dutycycle and frequency under the several household equipmentsoperated individually and simultaneously.

According to the graphs system is performed well underall loading and unloading conditions for specified values ofAP and Ts.

Settling time (Tset) was calculated as time required thevoltage to be 2% of the reference (set voltage).

All the time this value was under 1 second for all kinds ofappliance switching.

A. Line Voltage, Duty cycle, Frequency graphsfor switching Iron on and off

Vh

0)

0

230

220

210

200

190

180

170

160

1501 209 417 625 833 1041 1249 1457 1665 1873 2081 2289 2497 2705 2913 3121 3329 3537 3745 3953 4161 4369 4577

Time (50ms steps)

50

45

40

35

30

25

20

15

10

5

0

Dutycycle

IOn . *I-On 1w ll B)

*1 I-Off ..... ..I-Off1

1 230 459 688 917 1146 1375 1604 1833 2062 2291 2520 2749 2978 3207 3436 3665 3894 4123 4352 4581

Tirn ea6§QMs steps)

- Frequency

I -On I-Off I-Oi ... . I-OffLL40 -

35 -

30 -

1 231 461 691 921 1151 1381 1611 1841 2071 2301 2531 2761 2991 3221 3451 3681 3911 4141 4371 4601

Time (50ms steps)

Fig 7[A-C]. Voltage, duty cycle, frequency variations for switching electric iron [I] on and off

B. Line Voltage, Duty cycle, Frequency graphsfor switching Television on and off

-Vh240

220

a) 200

o 180

160

140

120

50-

45

40

, 35a,Z 30

0 25

20o 15

10

5

0

TV-off TV-off

1 224 447 670 893 1116 1339 1562 1785 2008 2231 2454 2677 2900 3123 3346 3569 3792 4015 4238 4461 4684 4907 5130 5353

Time( 50ms Steps)

Dutycycle

TV-On TV-On

1 203 405 607 809 1011 1213 1415 1617 1819 2021 2223 2425 2627 2829 3031 3233 3435 3637 3839 4041 4243 4445 4647 4849 5051 5253

Time (50ms Steps)

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-Freq

a)01)U-

1.1. 1. ~~~~~~~(C)

.h III IlI I

I I

Ou l%* l . t*+-. * -* *-*~~~~~~. 1

TV-Off TV-On TV-OffTV-On

401 200 399 598 797 996 1195 1394 1593 1792 1991 2190 2389 2588 2787 2986 3185 3384 3583 3782 3981 4180 4379 4578 4777 4976 5175

Time (50ms)

Fig 8[A-C]. Voltage, duty cycle, frequency variations for switching television on and off.

C. Line Voltage, Duty cycle, Frequency graphsfor switching Television on and offwhile Electric Iron is on.

-Vh

01)

0

1501 196 391 586 781 976 1171 1366 1561 1756 1951 2146 2341 2536 2731 2926 3121 3316 3511 3706 3901 4096 4291 4486 4681 4876 5071 5266 5461

Time (50ms Steps)

Dutycycle50

45- B40-

35-

30 IF

25-

10

5-

01 222 443 664 885 1106 1327 1548 1769 1990 2211 2432 2653 2874 3095 3316 3537 3758 3979 4200 4421 4642 4863 5084 5305 5526

Time (50 ms Steps)

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C,a

0

bu

-Freq

60-

58-

56-

54-

52-

(D 50-

48-

46-

44-

42-

40-

I-On I-Off .I-On

1 187 373 559 745 931 1117 1303 1489 1675 1861 2047 2233 2419 2605 2791 2977 3163 3349 3535 3721 3907 4093 4279 4465 4651 4837 5023 5209 5395

Time (50ms Steps)

Fig 9 [A-C]. Voltage, duty cycle, frequency variations for switching electric iron [I] on and off while TV is on.

IV. CONCLUSION

A new design for low cost micro-controller based voltagecontroller for micro scale hydro electricity generators werepresented. It was shown by the experimental result, for mosthouse hold appliances controller was stable and stay in thespecified voltage limits. Under sudden loading and unloadingconditions voltage level may overshoot from the referencebut from experimental results it shows that the settling timeis less than 1 second and also for most equipment switchingover shoot was remain behind the safety cut off limits.

Proposed design methodology involves the dynamic loadadjustment to compensate the load variations to keep thevoltage variations close the reference value most of the timeand with in specified threshold limits in all times.

Proposed system was tested for 2KW induction generatorand normal house hold equipment operations. The results ofthe design were quite encouraging and the proposedapproach can provide general design guide for buildingvoltage regulators for any micro scale hydro electricityvoltage generators.

ACKNOWLEDGMENT

Authors wish to thank Mr. Martin Wijesinghe for his kindsupport for the testing of the voltage regulator at hispremises.

REFERENCES

[1] Bhim Singh, S. S. Murthy and Sushma Gupta. "An improvedElectronic load controller for self exited induction generator in microhydel applications," Department of Electrical Engineering, Indianinstitute of technology, Delhi, Huaz Khas Delhi-16, INDIA.

[2] A Harvey & A Brown "Micro-hydro design Manual" ITDGPublishing, 1992.

[3] P Fraenkel, 0 Paish, V Bokalders, A Harvey & A Brown "Micro-hydro power: A guide for development workers," ITDG Publishing,ITPower,Stockholm Environment Institute, 1991.

[4] Nigel Smith "Motors as Generators for Micro-Hydro Power" ITPublications, 1994.

[5] Jeremy Thake "The Micro-hydro Pelton Turbine Manual: Design,manufacture and Installation for Small scale Hydropower", ITDGPublishing, 2000.

[6] C. Grantham, D. Sutanto and B. Mismaii "Steady state and transientanalysis of self excited induction generator", IEE Proc, Vol. 136, Pt. B.No. 2, pp.61-68, March 1989.

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