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WIND GENERATOR MONITORING AND CONTROL SYSTEM

Jakab Zsolt [email protected]

Submitted for the 2011 Digilent Design Contest

Cluj Napoca

08.05.2011

Advisor: Assist. Dr. Eng. Duka Adrian-Vasile

“Petru Maior” University of Tg. Mure ş

Wind Generator Monitoring and Control System Design Report

www.digilentinc.com page 2 of 19 Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.

System features - measurement of wind generator parameters (voltage, current, power consumption, wind speed) - voltage range: 7.5....24 V - current range: 0.1....11 A (adjustable) - wind speed range 0…….20. - microcontroller based systems - wireless radio communication between the wind generator system and the remote system - USB 2.0 communication with the PC - user application providing: data acquisition, data logging, plotting and display



Project Summary

1. Introduction

1.1 Problem to solve

1.2 Proposed solution

2. Hardware description

2.1 Wind generator system

2.2 Remote station

3. Software

3.1 Communication

3.2 Microcontroller applications

3.2 LabWindows CVI user interface Digilent Products Required

• 2 x PmodCLS

• 2 x PmodRF1



1. Introduction

1.1 Problem to solve

Small wind generators up to hundreds of watts work in parallel with chemical

batteries on 12 V, 24V or 48V direct current bus bar systems. A.C. consumers take

energy from these systems through inverters.

Wind generators deliver energy when wind speed exceeds a certain threshold

value prox. 3 - 5 m/s depending on the wind generator size. If wind energy is absent for

longer time, the accumulators start to discharge, and at a certain value the consumers

need to be disconnected from the d.c. bus bar and to be connected to other energy

sources, if available, in order to avoid damage in the energy storage system .This kind

of transition between energy sources can cause long interrupts in the consumers

operation, or even permanent shutdown.

In this conditions the main problem is the instability regarding the power

supplied by a small wind generator.

1.2 Proposed solution

In the idea of a parallel operation between a renewable energy source and a

relatively secure energy source, such as the public electric network, I suggest the

following monitoring and control system for a wind generator, built around Microchip

PIC microcontrollers:



2. Hardware description

The Wind Generator Monitoring and Control System is based on two subsystems: one

located near the wind generator and the other one placed away from the wind

generator’s site. These components are named:

- The wind generator system

- Remote system/station

2.1 Wind generator system - this part of the equipment has the following block diagram:

The system has its own power supply connected to the 12V dc. bus bar.

Energy can come in to the system from several sources: the wind generator, the

storage system (accumulator), the public grid or from all sources at the same time. The

source of the energy depends on the operating conditions, which the system has to

handle, coordinated by the microcontroller.

The main block is the PIC microcontroller, which takes signals from a wind speed

sensor and a measurement circuit, it processes them, the displays the results on the



Digilent's PmodCLS , it transmits the acquired system data to the remote equipment

and controls the C1 and C2 circuit breakers as described in the following table.

Wind generator system’s Control logic: state System events C1

state C2 state

Consumer’s main

energy source Cause

1 wind speed

normal current

normal voltage normal

closed open Battery + wind

generator There is sufficient wind speed, the load current

and output voltage are in normal limits

2 wind speed

normal current abow

normal voltage below

normal

closed closed Network + wind

generator The wind generator is working, the battery is

discharged due to overload

3 wind speed

below normal current

normal voltage normal

closed open Battery + wind

generator The wind generator is not working but the battery

is full charged

4 wind speed

below normal current abow


normal

closed closed Network Battery has discharged due to a persistent lack in

incoming wind energy

5 Any wind

speed current abow


normal + c2 closed

open closed 0 Consumer owerload , incoming energy from

network fails to bring the system to normal

parameters. Possible cause: inverter is defect

If case case 5 is reached the system remains stuck until the user removes all possible

defects and resets the system by the microcontrollers reset button.



The main components of the Wind Generator System are:

• Wind speed sensor also known as anemometer (home built) :

Principle of operation:

The disk and cup set are rotating on the same axes. Due to the holes on the disk's

periphery the fotodiode receives intermittent light from the LED placed on the other

side of the disk. Pulsating voltage arises on pin 2 of IC 74AC00, which is a NAND

Schmidt Trigger circuit. On output pin 2 of J1A connector a TTL level signal can be

collected and its frequency f measured with the PIC mcu.

The wind speed is computed as follows: v = 20 x f [m/s] , where 20 is the

wind speed sensor's constant.

Wind Speed sensor Operating range 0.3- 20 [m/s] .



• Power suply and measurement circuit

Supply voltage from dc. bus bar is applied to the main stabilizer IC 7805. To avoid

linking power supply against bus bar, polarization diode 1N 4148 was introduced after

a 250 mA fuse. When wrong connected the diode enters in conduction and short

circuits the fuse so the circuit is interrupted and no damage is produced.

IC 7805 assures the power supply for the PIC microcomtroller, anemometer,

relays, a 15 V double source for measuring circuit and a 3.3V source for PmodCLS and

PmodRf1.

The 15 V double source uses a d.c-d.c. converter to obtain the necessary

voltages for the LM 324 operational amplifier (op.amp.). The heart of the converter is a

classic astable configuration of two NPN transistors with the primary windings of the

transformer and a few discrete circuit components. 1N4148 fast switching diodes are

used to eliminate autoinduction spikes.

To measure the current one op.amp. with an amplification of approx. 100 is used

to get the voltage drop on the 0.0049 Ω shunt resistor.

Voltage on bus bar is measured using a voltage divider made using 10 kΩ and 33 kΩ

resistors.

The operating ranges for the measurement circuit are: voltage 7.5÷24 V, current 0.1÷

11 A

If malfunction occurs the outputs of the measurement circuit can't override



standard TTL level due to the use of 5V Zenner diodes connected on them. Also 10nF

capacitors are used to ground a.c. noise signals that may appear during wind generator

function.

• Microcontroller circuit

- uses a PIC 18F 4455 mcu for ADC and capture operation, UART and SPI

communication, and also performs system state control using relays .

Almost every I/O pin of the IC is protected by a 270 Ω resistor which limits the current

below 25 mA. Further 1 kΩ and 1.5 kΩ resistor dividers are used to interface PmodRf1

input pins with 5 V operating PIC mcu.

Transistor based amplifiers are used as relay drivers with protection diodes

against autoinduction voltage.

Buttons, LED's, Digilent’s PmodCLS LCD, and sockets are included for handling the

system. Relays are not on the pcb because of their size.



Picture of the Wind Generator system

• The generator

- home built generator with

rectifier and electronic charging

relay included .

To produce the magnetic flux,

permanent magnets are used



The power supplied by this generator is up to 400W depending on the speed of

the wind. The system was tested by the author up to a power of 250W (v=5m/s)



2.2 Remote station

Uses a PIC microcontroller to interface the

PmodRf1 transceiver with the PC, and also offers the

capability of data display on the Digilent PmodClS

module. SPI, UART and USB links are used here for data

transfer.

On the PC an application developed in

LabWindows CVI performs data processing, storage

and displays different tasks. Power supply for this system is taken from the

PC's USB port or from another compatible source. A 3.3

V stabilizer ic supplies the PmodRf1 and PmodCLS

module. Two buttons and two LED's were provided to

be available for handling durrig programming and for

debugging purposes.



3. Software

3.1 Comunication

UART, SPI, USB and Radio link communication were implemented as follows:

- between both PIC mcu's and PmodCLS's a 32 byte data packet is transmitted with

UART protocol;

- between both PIC mcu's and the Digilent PmodRF1's , an software implemented SPI

interface is used

- between the remote station and the PC an USB connection is used

- between the wind generator system and the remote station a unidirectional radio link

is used for the data transfer

3.2 Microcontroller aplication

The application on both microcontrollers were developed using MPLAB IDE

On both mcu's after initializations and configuration of peripherals the program enters

in a loop.



On the remote system's mcu the loop starts with the reception of data from the

radio link. If there is no data available the system displays "No data" and if 32 byte

data package is received the voltage, current ,power, and wind speed numerical values

are displayed.

In 1 sec. time periods (by testing Timer0 IF flag bit) USB data transmission to Pc is

executed.

On the wind generator system's mcu the loop begins with the data acquisition,

then the voltage, current, power and wind speed values are displayed. After that, the

mcu checks if the values are within their normal limits and if not it tries to establish the

normal parameters in the circuit by controlling the circuit breakers. After performing

system control the mcu sends the data to the remote station using the PmodRf1.

This loop is not infinite. If the mcu can't bring back the system to its normal

parameters within 1 min. from its first action on the circuit breaker (C2), the loop

stops at the system’s command and removes the load from 12V bus bar through C1

circuit breaker.

3.3 PC aplication (LabWindowsCVI)

The monitoring and data acquisition program has the following main user interface :

The first developed version of the wind generator monitoring and control system (.v1)



uses wired UART communication (a cable connection) between Pc and the generator

system. The final version of the system (.v3) uses a virtual USB com port based on a

firmware provided by Microchip for PIC controllers. This means that the

communication with new system is possible without major hardware or software

impact.

The main user interface contains 4 analog and 4 digital measuring instruments,

text messages, LEDs, buttons and also displays the current time and date.

The "New Acq" button starts a new data acquisition if no other acquisition is in

progress. For this the user must select the acquisition interval, period and the name of

the file in the settings box which appears at start-up. If no name is introduced the file

will have the current date as a name:

If

the

name already exists a prompt message alerts the user:



Overwriting a file is not possible and if the user does not change the introduced name

no acquisition will start

When creating a new acquisition two files are created in the project’s folder, one

*.txt file and one *.ccmte file. Both files are read only. The first file type can be

opened with any file handling program, and the second one is used only by the

application to store data needed for plots and graphics.

To view results on a graph the user selects one of the plot buttons on the main

user interface. A file selection window appears with a list of available files:



After selecting a file, the plot is shown in a new window with the generic name "Plot":

For selecting other files from the list an "Open file" button is provided on the

window.



References

(1) Electronică de putere - Doru Suciu (2) Dispozitive electronice si electronica analogica Lucrări de laborator (UPM)- GERMÁN-SALLÓ Zoltán

(3) Sisteme cu microprocesoare. Îndrumător de laborator (UPM) - Duka Adrian, Jovrea Titus

(4) Programarea interfeţelor îm LabWindows. Îndrumător de laborator (UPM) - Haller Piroska, Duka Adrian Vasile, Rusu Marius Sebastian

(5) Wind Energy Handbook -Tony Burton, David Sharpe, Nick Jenkins, Ervin Bossany

(6) http:// www.hobbielectronika.hu



Appendix A:

• Source code files : - monitoring station: CCMTE_RadioPC.c - wind generator system: CCMTE_Radio_T.c

• CVI application: CCMTE_CVI - CCMTE_CVI.001 - CCMTE_CVI.002 - CCMTE_CVI.exe - setup

wind generator monitoring and control system_jakab zsolt

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