invertor 200w

Development of AC Inverter stage of 200W Off-Grid Microinverter for Photovoltaic Application

Kyu Kyu Mar, Maung Maung Latt, Zaw Min Naing

Abstract This 200W solar microinverter consists of three portion: the MPPT, the DC-to-DC step-up converter and the DC-AC Inverter sections. The MPPT detects and optimizes the power from the solar panels by using of microcontroller to achieve the maximum power transfer from the panel at any instant of the time. DC voltage output of MPPT is driven to the DC-to-DC converter. Small size soft ferrite core is used as a power converter at 65 kHz in DC-DC step-up converter. This paper especially discusses on the third portion of the microinverter stage of off-grid type. The inverter delivers 230VAC, 50 Hz modified sine-wave. The overload and short-circuits protection circuitries for the output is also provided. The battery-less system provides the green power generating process and environmental friendly.

KeywordsMPPT, DC-DC step-up converter, Soft Ferrite Core, Inverter, Protection.

I. INTRODUCTION

HERE are two important sections in Microinverter System, so called the MPPT section and inverter section.

Solar Panel

Switching & Output

PVV & I Sensor

PIC 16F873

FET Driver

Output V & I sensor

DC to DC Step-Up

Converter

PWM Control

DC to AC Inverter

Switching Control

Oscillator

MPPT

VINI IN VOUT IOUT

13.5Vdc

340Vdc

LM358

AC 230V, 50HzModified Sinewave

Output

Fig.1 Block Diagram of Microinverter System F. A. Kyu Kyu Mar, is with the Electronic Engineering Department,

Mandalay Technological University, Mandalay, Myanmar (e-mail: [email protected]).

S. B. Maung Maung Latt, is with Pro-rector, Technological University (Meiktila), Myanmar (e-mail: [email protected]).

T. C. Zaw Min Naing, is with Pro-rector, Technological University (Maubin) , Myanmar (e-mail: [email protected]).

Microinverter system is one of the first of these products obtainable on the market. It is a set of small units that attach directly to each solar module to change DC power into AC power. It transmits precious performance data on each module to the system possessor. The result is more power, a more reliable system, and the ability to monitor and respond quickly to performance issues. Homeowners and business-owners get more energy, lower costs, and greater control of their solar investment [6].

II. THE INVERTER SECTION

The inverter consists of Power MOSFET Inverter Bridge

(Q12~Q15), Driver Stage (Q8~Q11), Switching Control Stage (U10), Pulse Generator & PWM control stage (U9-556), Overload protection & Short-circuit protection (U11A&B) and Thermal protection (U11C) stages.

R4710K

R51

470k

+ C4810uF / 50V

D181N4148

R38 4k7

R46ZERO

-

+U11C

LM339/c

9

814

U9B

LM556/b

11

913

81210 CV

OUTDSCHG

TRGTHRESRST

U10A

4013/a

5

3

12

14

6

7

4

D

CLK

QQV

DD

S

GN

D

R

ThermalProtection R61 22k

R63

10k

Q162N2222

-

+U11D

LM339/d

11

1013

31

2

R50 47k

VR120k

SK1

AC Outlet

Q10MPSA44

-

+U11A

LM339/a

7

61

+C44

2.2uF / 50V

230V,50Hz

C51100nF

Q92N2222

R434k7

R39 4k7

D212.5V Zener

U10B

4013/b

9

11

1312

810

D

CLK

QQ

SR

R64

10k

100Hz

Overload&Short-circuitProtection

R60

36k

D17PR1504

C53100nF

Q112N2222

+12Vreg.

C54100nF

R360.33 / 1W

+C46

10uF /50V

Q15IRF830

-

+U11B

LM339/b

5

42

DC- to - DC Inverter

Control GND

Power GND

Control +12VDC

Power +340 VDC

Freq. Adjust

R59

1k

R55

3k3

R49 15k

R58

130k

+C45

2.2u f / 50V

R52

10k

C49

1nF

OutputVoltageAdjust

+C47

22uF / 50V

R56

10k

C50

100nF

R54

27k

4013

U9A

LM556/a

3

7

51

14

624 CV

GN

D

OUTDSCHG

VC

C

TRGTHRESRST

R53

180k

D201N4148

VR250k

Q14IRF830

R4843K

Q13IRF830

100Hz

R44

10k

R424k7

R40 10k

R57

TS1

R45

10k

C52100nF

Q12IRF830

Q8MPSA44

R41 NTC

NE556

R62

22k

C55100nF

D19PR1504R37

1M3 / 0.25W

Fig.2 The DC-AC Inverter Circuit The Power +340VDC output from DC to DC inverter stage

is applied to the power inverter bridge and control +12V regulated DC voltage is applied to control IC circuitries.

U9 (NE556) Fig. 3 acts as frequency generator and PWM control circuit. It has 2 timer stages. The first timer is used as astable multivibrator which output frequency is exactly 100Hz. This frequency is determined by R58, VR1, R59 and C52. 100Hz pulse is appeared on Pin5 of U9.

T

International Conference on Advances in Electrical and Electronics Engineering (ICAEE'2011)

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C55100nF

0 V

C53100nF

100Hz

PWM Out Put

100Hz

C54100nF

+12V

R59

1k

+340V

NE556

Freq. Adjust

R58

1.5MVR120k

U9A

LM556/a

3

7

51

14

624 CV

GN

D

OUTDSCHG

VC

C

TRGTHRESRST

U9B

LM556/b

11

913

81210 CV

OUTDSCHG

TRGTHRESRST

C52100nF

VR250k

R60

36k

OutputVoltageAdjust

R58

130k

Fig.3 Oscillator and PWM Circuit

The second timer acts as monostable multivibrator. The

output from the first timer is triggered to second timer so that the interrelated impulse is occurred at output Pin9. The pulse width of this output impulse depends on the voltage across C40 (i.e, +340VDC). This pulse width is controlled by R37, R60, VR2 and C55. Adjusting VR2 (PWM control) results to varies the output AC voltage of inverter stage.

One of the output from the U9 (Pin9) Fig. 4 is driven directly to the input of U10 (Pin3) and the other input (Pin11) is driven by the 180 phase shift circuit which consists of Q16, R61 and R62. U10 consists of 2 separate D-flip-flops. The four 50Hz square-wave outputs (on-off time ratio 1:1) of the two flip-flops (Pin 1, 2, 12, and 13) are driven to the driver stage(Q8~Q11).

Control4

Disable

Q162N2222

R62

22k

Control3

4013

Control2

U10B

4013/b

9

11

1312

810

D

CLK

QQ

SR

0 V

U10A

4013/a

5

3

12

14

6

7

4

D

CLK

QQVD

D

S

GN

D

R

100Hz

+12V

PWM Out Put

Control1

R61 22k

Fig.4 Control Pulse Drive

The driver transistors are controlled the switching sequence

of the power MOSFET bridge and the modified sine wave output AC voltage is obtained from the AC outlet.

U11 (LM339 quad comparator) Fig. 5 is used as the protection circuit. The open collector outputs of U11A, B & C are formed as parallel-operated circuits. In normal situation the capacitor C48 is charged via R51 and the comparator U11D output (Pin13) is in low (L) state. If the comparator U11A and/or U11B and/or U11C output become low-state, the capacitor C48 will discharge, then the U11D output will

change to High-state (H), and hence, the reset signal is sent to U10 and the inverter bridge will be closed.

R55

3k3

R40 10k

C50

100nF

R48 43k

Overload&Short-circuitProtection

R54

27k

+C47

22uF / 50V

R50 47k

-

+U11D

LM339/d

11

1013

312

R46

4k7

-

+U11B

LM339/b

5

42

R49 15k

-

+U11A

LM339/a

7

61

R51

470k

R57

TS1

ThermalProtection

From Current Sensor

+12Vreg.

+ C4810uF / 50V

R52

10k

0 V

+12V R47 10k

+C46

10uF /50V

R53

180k

D212.5V Zener

Disable

C49

1nF

-

+U11C

LM339/c

9

814

R56

10k

Fig.5 Over Voltage and Over Current Protection Circuit

U11C and associated components are act as thermal

protection circuit for the output MOSFET stage. The temperature sensor TS1 is mounted on the heat-sink of the output transistors. The voltage divider R53 & R56 set the constant voltage on input Pin8. The temperature surveillance voltage is applied to input Pin9 from the voltage divider which consists of R55 & R57 (TS1-temperature sensor). The hysteresis function is determined by R53.

U11A & U11B are formed as overload & short-circuit protection circuit. R46 & D21 provide the reference voltage (+2.5V) to the comparators' non-inverting inputs. R36 is the shunt resistor of the power stage and the corresponding negative shunt voltage is applied to the non-inverting inputs via R47 & R49. If the summing voltage of these inputs is smaller than 0 V, U11B will interrupt the power stage through U11D.

The function of U11A is the same as U11B and this stage is the overload protection stage.

III. DESIGN OF DC-AC INVERTER

A. Design of Oscillator

R2

C

LM556/a

3

7

51

14

624 CV

GN

D

OUTDSCHG

VC

C

TRGTHRESRST

100nF

+12V

R1

0 V Fig.6 Astable Mode Design Fig.7 Component Selections

For typical value, it would be chosen C for 0.1F (100nF).


152

The duty cycle can be calculated as

21

2

2RRRD+

= (1)

The required output frequency is 100 Hz and must be pulse.

So R2 is much smaller than R1. If R2 = 1k, R1 must be calculated as

CRR

f)2(

44.1

21 += (2)

21 244.1 RfC

R = (3)

= kR 1421 From the component selection Fig. 7, it can easily find the

intersection point of C and frequency of 100 Hz. It is found that the value of R1+R2 must between 100k and 1M. From calculation R1+R2=143k, so it would be chosen

R1= 142 k and R2= 1 k. For convenience of adjusting exactly 100 Hz on output, R2

is substituted with series connection of 130k and 20k preset resistor.

As per data sheet, the control voltage terminal (pin 3 of 556) is chosen 0.1F. B. Design of PWM Circuit

The PWM control circuit is designed with another timer of 556. The timer is in monostable mode and the control pulse train is applied to trigger terminal of timer. (Pin 8 of 556)

NE556 utilizes the separated & regulated 12VDC from previous stage. To control the power inverter output voltage, the DC voltage input of inverter bridge must be sensed to PWM circuit and is applied to the timing components R1 & C series circuit. To maintain the maximum charging voltage not exceed to 12VDC, R2 is parallel connected to C. R1 and R2 act as voltage divider.

0 V

+340V

LM556/b

11

913

81210 CV

OUTDSCHG

TRGTHRESRST

Pulse 100 Hz Input

R1

C100nF

PWM Output

R2

Fig.8 Monostable Mode with Trigger Input & Timing Chart

If the bleeding current of 0.2mA is chosen, R2 = 12V/ 0.2mA = 60k, 2.4mW and so the resistor R2 = 56k, 0.25W is chosen. In practice, for fine

adjustment for output AC voltage of inverter bridge, better using pre-set resistor instead of fixed resistor. For convenience

it would be chosen 36k (fixed) + 50k (pre-set) resistors. And so

R1 = (340-12) / 0.2mA = 1640k, 65.6mW, For the delay time of 200ms, 111.1 CRt = (4)

FC 101.01 = As per data sheet, the control voltage terminal (pin 11 of

556) is chosen 0.1F.

C. Design of Inverter Pulse Driver The 4013 CMOS IC has dual type D flip-flop and it can get

two pair of phase-shifted pulse for inverter bridge control. The type D flip-flop in divided-by-two configuration is

presented. The output frequency is half of the input frequency. And used another D flip-flop for 180 out-of phase control

and the transistor Q acts as the phase-shifter The Enable/disable points are connected together and

controlled by the protection circuit section. The pulse drivers are used with NPN switching transistors and having typical values of 4.7k load resistors and 10k base resistors.

The final pulse driver circuit will be seen as below.

Q8

0 V

PWM Out Put

+12V

100 Hz

R63 10k

0 V

+12V

R39

4k7

R62

22k

U10A

4013/a

5

3

12

14

6

7

4

D

CLK

QQV

DD

S

GN

D

R

R42

4k7

R43

4k7

Control2

Control3

R61 22k

+12V

Q9

Enable/disable

R64 10k0 V

0 V

Q11

4013

Control1

R45 10k

0 V

Q162N2222

Q10

R44 10k

R38

4k7

U10B

4013/b

9

11

1312

810

D

CLK

QQ

SR

Control4

Fig.9 Inverter Bridge Pulse Driver Circuit

D. Design of Inverter Bridge

The peak voltage is 340VDC and it is chopped by MOSFET to have 50 Hz, 240VAC maximum. For the output of 200W power, the maximum current is delivered as 0.83A.

If only 2W of heat energy is produced by MOSFET switches, the maximum value of RDS(on) is 2 / (0.83)2 = 2.9. From the FET Selection Chart, the N channel power MOSFET of IRF830 from Philips Semiconductor meets these specifications:


153

Q15IRF830

SK1AC Outlet

0 V

Control1

Q13IRF830

Control4

R41 NTC

+340V

Control2

Control3

Q12IRF830

Q14IRF830

230V,50Hz

Fig.10 Inverter Bridge

VDSS = 500V, ID = 5.9A and RDS(on) 1.5 And so it would be chosen IRF830 for the switching device. The NTC resistor is connected in series with AC load

to protect the electric shocked hazards to the user.

E. Design of Protection Circuit The over current and output short-circuited protections are

included in this inverter. The simplified design diagram is shown in Fig. 11. Four comparators are used in this circuit and so the quad-

comparator IC of LM339 is the heart of protector. A & B comparators are used as OC and SC protectors and C comparator is used as thermal protector which sensing device (thermister) is mounted on heat-sink of the power MOSFETs. And these three comparator outputs are summed together into another inverting comparator D. Then this last comparator output is controlling the inverter bridge working status. (enable / disable)

SK1

AC Outlet

+12V

-

-

+U11C

LM339/c

9

814

+3.3V ref

DC-DCConverter

-

+U11D

LM339/d

11

1013

312

Inverter CircuitCurrentSensor

Enable / disable Inv erter

-

+U11A

LM339/a

7

61+2.5V ref

+340V

+2.5V ref .

-

+U11B

LM339/b

5

42

+12V

+12V

+

Thermister(on Heatsink)TS1

Fig.11 Protection Circuit Setup Diagram

In normal states, outputs of comparator A, B and C are

positive with respect to ground. Even one output of these goes low, the comparator D output goes high and disables the inverter bridge.

When there is no-load condition, there is no current flow to the inverter bridge. So no voltage drops across sensor. A 2.5V reference is applied to the comparator inverting terminal via R1. The sensed voltage is also applied to this terminal via R2.

+

Vsense

+

-

+U11B

LM339/b

5

42

R1

-

control

+2.5V ref .

-

-

+340VDC

+12V

0V

R4V1

V2

Inverter Circuit

R1

R2

+

Fig.12 Over Current Protection

Let V2 = 0.5V (beyond 0.6V; not to conduct internal

clamping diode in LM339). That means VRs + VR2 = 0.5V. When normal 240VAC, 200W inverter output, the current

flow is 0.83A. If 150% of this current is defined as over-current, it will

equal 1.245A. To cancel the V2, the sensor resistor must be 0.5 / 1.245 = 0.4, 0.62W.

Set bleeding current through R1, R2 and RS is 50mA, when no inverter current is flowing in sensor,

(R1+ R2 + RS) =Vzener/Ibleed = 2.5V / 0.05A = 50k. And R2 = 0.5V / 0.05A = 10k, 0.025W. And R1 = 50-10-0.33 = 39.67k, 0.1W. By E24 series, chose R1 = 43k, 0.1W. For output open-

collector resistor, chose 470k typical value. The configuration of short circuit protection circuit is same

as above and base on 200% of excess current and got the values of

R1 = 47k, 0.25W and R2 = 15k, 0.25W. And the summer-inverting comparator and thermal protector

is designed with data sheet typical values.

IV. EXPERIMENTAL RESULTS OF CONSTRUCTED HVDC AND DC-AC STAGES

The complete prototype DC-to-DC converter is shown

below [2].

Fig.13 DC-DC Step-Up Converter


154

Fig.14 Inverter Circuit

This result is shown no load test of HVDC to 230VAC

modified sine wave output in Fig. 15.

Fig.15 Measured Results of no load test of HVDC to 230VAC

The complete prototype is load test of HVDC to 230VAC

modified sine wave output as followed. In the method of testing with 12V100Ah battery instead of

solar cells without using MPPT section, it is seem that the output AC voltage is very stable in full rated load of 200W.

Fig.16 Measured Results of Load test Inverter

V. CONCLUSIONS In this paper the operation, design and considerations of an

inverter stage of 200W off-grid microinverter is presented. The prototype circuit boards for MPPT, DC to DC converter and inverter are individually constructed on perforated boards. The ferrite transformer not only to increase the converted DC power but also only small spacing requirement is provided [2]. The solar panels must be paralleled to meet the input requirement of MPPT section. The future task is all of the above three sections must be integrated in single PCB and attached additional sections, such as phase detection of output AC for the capability of two or more microinverters in parallel connection to increase output power and the control and supervisory data and the accessed via AC output line to the PC network.

All the designed functions such as protection, over-voltage, overload, overheat etc was found satisfactory. Further tests are still being done and more attention is given to reduce the production cost even more.

ACKNOWLEDGMENT

The author would like to Special thanks are due to her Supervisor, Prof. Dr. Maung Maung Latt, Pro. Rector, Technological University (Meiktila), Prof. Dr. Zaw Min Naing, Pro. Rector, Technological University (Maubin), and to her teacher, U Soe Hlaing,(MRES)-Myanma Renewable Energy System, for their useful guidance, patience and giving valuable ideas. The author greatly expresses her thanks to all persons whom will concern to support in preparing this paper.

REFERENCES

[1] D. M. Kammen: Innovations in Solar Energy R&D and PV, 4th Germany California Solar Day, May 27, 2008.

[2] Kyu Kyu Mar: Implementation of DC-DC step-up converter design for 200W off-Grid Microinverter, Second ICSE Conference, Yangon, Myanmar, December (2010) 67-71.

[3] R. W. Erickson: Fundamentals of Power Electronics, New York: Chapman and Hall, 1997.

[4] J. David Irwin: Power Electronics Handbook, 2001, Academic Press. www.powersystemsdesign.com [5] D. Jim, E. Dan, and S., Jeremy: DC-AC Pure Sine Wave Inverter, 2006. [6] J. Jvd. Merwe: 150W Inverter- An Optimal design for use in solar home

system,2005.

.


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Abstract Field trial is very critical and high risk in autonomous UAV development life cycle. Hardware in the loop (HIL) simulation is a computer simulation that has the ability to simulate UAV flight characteristic, sensor modeling and actuator modeling while communicating in real time with the UAV autopilot hardware. HIL simulation can be used to test and validate the UAV autopilot hardware reliability, test the closed loop performance of the overall system and tuning the control parameter. By rigorous testing in the HIL simulator, the risk in the field trial can be minimized in research and development UAV autopilot. This paper presents a practical approach of applying an Inertial Navigation System (INS) using MEMS inertial sensors, Global Positioning System (GPS) receiver for the Guidance, Navigation and Control (GNC) of an autonomous Unmanned Aerial Vehicle (UAV). And the HIL environment can give the best results by comparing with practical unmanned fight test.

Keywords Hardware In the Loop Simulation, unmanned air vehicle (UAV); micro-electro mechanical system (MEMS); global positioning system (GPS); Flight control; Navigation and Guidance (GNC)

.

I. INTRODUCTION NMANED air vehicles are nowadays seen as an area of great importance in the aerospace industry. Unmanned Aerial Vehicle (UAV) has proved to be a very valuable

asset in military and commercial application includes reconnaissance, surveillance, search and rescue, remote sensing, etc. UAV can accomplish its mission without risking the pilot/operator and usually with lower operational cost compared to manned aircraft.

In order to become successful, the cost of these systems has to be affordable. Generally, the construction of UAVs is costly and time consuming. Safety is thus a primary issue that one is facing in conducting actual flight tests. As such, intensive testing and simulation, especially with the actual UAV hardware in the simulation loop, is an effective way to

Dr.Thae Maung Maung, Aerospace Reserach Section, Myanmar Aerospace Engineering University, Myanmar (phone: 095-64-35241-35201; fax: 095-64-35245; e-mail: thaemaungec@ gmail.com).

Dr Hla Myo Tun, Department of Electronics, Mandalay Technology University, Myanmar (phone: 95-09-5416337; e-mail: hlamyotunmtu@ gmail .com).

Moe Kyaw Naing , Aerospace Reserach Section, Myanmar Aerospace Engineering University, Myanmar (phone: 095-64-35241-35201; fax: 095-64-35245; e-mail: vincentmoe@ gmail.com).

detect and prevent unnecessary malfunctions of hardware, software and automatic flight control systems. Hardware-in-the loop simulation is a real-time simulation method or frame work, in which the UAV platform is reacting the same way as it in the real experiment. Using such a method, researchers can effectively evaluate the reliability of the overall UAV system. In particular, the framework can be intensively used to examine the performance of designed automatic flight control algorithms. Necessary enhancements and modifications can then be done before actually testing the UAV system in the sky and thus the probability of test flight accidents can be greatly minimized. Thus researching on the Guidance, Navigation and Control (GNC) of a UAV using MEMS sensors is important. The physical UAV system comprises of the flight platform, onboard systems, communication links, and ground station. The UAV states are down linked to the ground station for real time monitoring and to provide accurate and reliable 3D navigation solutions as well as to perform the guidance and control task. In my university Research and Development center in Myanmar Aerospace Engineering University (MAEU) objective is to develop a fully autonomous UAV control system which is low cost ,simple to operate, modular, and reliable for unmanned technology see Figure 1. For these requirements, the Hardware In the Loop system is a very useful simulation tool.

Fig. 1. Block Diagram for MAEU 01 UAV system

II. UAV DEVELOPMENT LIFE CYCLE The steps taken in this UAV development life cycle are:

Airframe selection, Guidance, Navigation and Control development,

Navigation Guidance and Control System using Hardware in the Loop Simulation for Unmanned

Aerial Vehicle (UAV) Dr. Thae Maung Maung, Dr. Hla Myo Tun, and Moe Kyaw Naing

U


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invertor 200w

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