wind generator monitoring and control system_jakab zsolt

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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. Mureş

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 voltage below normal

closed closed Network Battery has discharged due to a persistent lack in incoming wind energy

5 Any wind speed current abow normal voltage below 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] .



• The 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 The 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 application 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. If the mcu can't bring back the system to its normal parameters within 5 sec. from its first action on the circuit breaker (C2), the system’s control 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 interfețelor 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 ‐ Programul CCMTE_CVI se instalează folosind executabilul setup şi nu necesită decât drepturi de administrator pe pc‐ul in cauză.

wind generator monitoring and control system_jakab zsolt

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