Design and Implementation of a Renewable Energy ... - IEEE Xplore

4th International Conference on Power Engineering, Energy and Electrical Drives

Istanbul, Turkey, 13-17 May 2013

Design and Implementation of a Renewable Energy Monitoring System Ersan KABALCI*,1, Alper GORGUN2, Yasin KABALCI3 *,1

Department of Electrical and Electronics Eng., Engineering and Architecture Faculty, Nevsehir University, Turkey. Department of Electronics and Automation, Vocational College of Haci Bektas Veli, Nevsehir University, Turkey 3 Department of Electronics and Automation, Nigde Vocational College of Technical Sciences, Nigde University, Turkey. [email protected], [email protected], [email protected] 2

Abstract— This paper introduces an instant monitoring infrastructure of a renewable energy generation system that is constituted with a wind turbine and solar panel arrays. There an uncontrolled six-pulse rectifier converts ac output voltages of wind turbine to dc. The hybrid system of renewable energy sources (RES) couples generated voltages of wind turbine and solar panels on a dc-bus and supplies charge voltage to the battery bank. The monitoring platform is based on current and voltage measurements of each renewable source. The related values are measured with the developed sensing circuits and are processed by an 18F4450 microcontroller of Microchip. The processed parameters are then transmitted to a personal computer (PC) over universal serial bus (USB) to be saved in a database and to observe the system instantly. The observing software that is coded with Microsoft Visual Studio.Net platform allows system administrator to monitor generated energy and actual status of each renewable energy source at a glance. The coded visual interface of monitoring software can manage the saved data to analyze daily, weekly and monthly values of each measurement separately. Keywords-hybrid renewable energy; wind turbine; solar panel; monitoring; microcontroller.

I.

INTRODUCTION

The renewable energy sources (RES) such as wind, solar, biomass, geothermal, and tidal are believed to tackle the dependency to fossil fuels in this century. The RES are also assumed as alternative energy sources and are integrated to current grid structures by distributed generation (DG) systems. The island mode applications of RES are being converted to grid-tied integrations in order to increase the capabilities of conventional grids [1,2]. The DG based on various energy sources will allow obtaining higher total energy efficiency and improved performance. A robust micro grid constituted with different energy sources should also exhibit an operation capability similar to “plug and play” structure. This term means the integration capability of any additional source connected to existing DG system without requiring any system configuration. There are many ways to integrate different renewable energy generation sources to form a hybrid system. The methods can be generally classified into three categories as dccoupled, ac-coupled, and hybrid-coupled [1-3]. The monitoring and metering requirements in DG networks should be performed as well as done in conventional networks. Although

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there are several methods proposed as wired or wireless measuring, all the solutions are related to smart grid concept that is extensively researched [5-7]. The demands directed to a smart grid are remote sensing, communication, control, monitoring and analysis processes. The smart grid should also meet these requirements in a sustainable, reliable and efficient way. The applications and studies on smart grid are mostly focused on phase measurements, advanced metering and remote monitoring of a source [7]. The RES system introduced in this study is based on dc-bus coupling by rectifying the output voltages of wind turbine and connecting to dc-bus of solar system as shown in Fig. 1. The monitoring system is developed with sensing and measurement circuits. The current and voltages of wind turbine and solar panel array are measured instantly and are processed with a peripheral interface controller (PIC) of Microchip. The parameters to be observed are acquired with sensing circuits that are constituted by current and voltage sensors. The acquired values are conformed to the involved levels in order to be processed by microcontroller (MCU). The pre-processed measurements are then applied to analog-digital conversion (ADC) ports of the MCU. The key role of the MCU is performing the connection between personal computer (PC) and measurement system where monitoring software runs on the PC to save and analyze the actual conditions of RES. A bidirectional universal serial bus (USB) connection is managed by the MCU. The interface software that is coded by using Microsoft Visual Studio.Net platform provides to save measured data to a database by generating historical view options and visualizes saved data on user interface with

Fig. 1. Schematic diagram of the hybrid energy system.

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graphical presentations. The following paarts of this paper covers introduction of the RES test-bed, measurement and monitoring system in second and third parts,, respectively. The operation analyses and evaluation of the syystem performance are discussed in fourth section. II.

THE IMPLEMENTED RENEWABLE ENERGY SYSTEM

The hybrid RES that is constituted with a wind turbine at 2 kW rated power and a solar panel arrayy are installed at Vocational College of Haci Bektas Veli as seen s in Fig. 2. The rotor diameter of wind turbine is 3.6 m and hub height is 9 m. The over speed protection is supplied withh electromechanic braking and dump load methods. The cut-in speed of turbine is 3 m/s while the cut-off limit is set to 20 m/s.. The wind turbine generates three-phase ac output voltage arounnd 165 V owing to its permanent magnet synchronous generator (PMSG). The solar energy conversion system iss constituted with eight mono-crystalline solar panels as seen on o the upper righthand side of Fig. 2. The solar panels are connnected in serial and parallel configuration in order to share power p capacity in voltage and current distribution. The generaated power of the RES is coupled to dc-bus and is used to chaarge batteries. The battery bank consists of eight serially conneccted 12V/100A gel batteries. The control and monitoring system m illustrated in Fig. 1 performs charge control operation of the enntire system. There sensing and MCU circuits as seen in Figg. 3 implement a monitoring system. III.

RING SYSTEM IMPLEMENTATION OF MONITOR

The software and hardware that are desiggned to acquire the related measurements of solar and wind power p system are analyzed in this section.


measurement and communicaation circuits require ±5V and ±12V voltage levels. Fig. 4 illuustrates the supply circuit that is built with symmetrical voltage regulator r circuits. B. Current and Voltage Acquissition Circuit The current acquisition circcuit is based on LA55-P current sensor of LEM that has a convversion ratio at 1/1000 [8]. Since the measurement values of currrent circuit will be quite low, the sensitivity of the data that willl be transferred to the MCU is also expected to be low. Thhere is an active amplifier is designed to overcome this situation. The current data acquisition circuit is shown in Fig. F 5 where the current of solar panel is obtained with currentt sensor in a dc waveform and amplified with an operationnal amplifier (op-amp). The amplified dc waveform is appplied to RA1 pin of the MCU. Furthermore, a potentiometer and zener diode is used on the input side of the MCU to t provide protection against overshoots. Another current accquisition circuit is designed as seen in Fig. 6 for wind turbinne and conversion system. The current of wind turbine is acquuired with current sensor in a dc waveform as done in solar systtem and is amplified with an opamp to transfer the signal to RA A3 pin of the MCU. The overshoot current prottection of wind data acquisition system is performed with a pootentiometer and a zener diode that are connected parallel to RA3 R pin of the MCU as seen on the right-hand side of Fig. 6. The voltage acquisition circuit designed for wind turbine convverts the measured value to a dc waveform and then provides to RA2 pin of the MCU by amplifying. The zener diode is i also added to this circuit for protection issues where the com mplete circuit is seen in Fig. 7.

A. Supply Circuit The voltage supply circuit is designed inn order to provide the required voltages in symmetrical vaalues. The MCU,

Fig. 3. Block diagram m of the control system.

Fig. 2. Hybrid RES installed at Vocational College of o Haci Bektas Veli.

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Fig. 4. Schematic diagram m of voltage supply circuit.

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Fig. 5. Current acquisition circuit for solar panels.

Fig. 8. The flowchart of MCU.

Fig. 6. Current acquisition circuit for wind turbine.

Fig. 7. Voltage acquisition circuit for wind turbine.

C. Control Circuit 18F4450 microcontroller is known as USB microcontroller with nanowatt technology. The PIC18FX455/X550 device family contains a full-speed and low-speed compatible USB Serial Interface Engine (SIE) that allows fast communication between any USB host and the PIC® microcontroller. Besides being compatible to USB2.0 protocol, 18F4450 MCU provides 1.5Mb/s data communication speed in low speed mode and 12Mb/s speed in full speed operation mode. There are 22 separate registers that are named as USB Control register (UCON), USB Configuration register (UCFG), USB Transfer Status register (USTAT), USB Device Address register (UADDR), Frame Number registers (UFRMH:UFRML), and Endpoint Enable registers (UEPn) are defined to control USB communications [9]. The control circuit is constituted with an 18F4450 owing to these features and performs the real time measurement of all hardware besides control operations.

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The block diagram seen in Fig. 3 illustrates the control circuit and its integration to energy conversion system. All the data sent from measurement and acquisition devices are evaluated by the MCU. It is observed by experimental studies that the MCU performs the operation of system parameters in a fast and reliable way owing to its software developed in C programming language. The MCU senses its configured ports continuously and awaits an input waveform to convert to the data. This sensing property of the MCU is also related with a PC over USB connection and the MCU operates the command arrays that are sent from the PC. In case of a command is sent from PC to MCU, it operates the related sub-procedure and writes the obtained values to the database. The flowchart of the MCU is shown in Fig. 8. These operation procedures are synchronized by control signals that are managed by MCU with USB port. Each transmission cycle is depended to USB authorization that enables MCU to send data package containing four parameters in serial communication standards. Although the communication speed between USB and MCU can be increased up to 480 Mbit/s owing to USB 2.0 protocol, it is limited to 12Mb/s by the full speed oscillator of 18F4450 MCU. IV.

DEVELOPED MONITORING TOOL

The hardware design of the monitoring system is seen in Fig.9. The voltage and current measurement board that is depicted on the left-hand side of Fig.9 is built with LA-55P current sensors and LV-25P voltage sensors. “Attenuating Circuit” decreases the sensed wind turbine voltage and all the voltage and current values are converted to dc voltage levels by “Measurement and calibration circuit” where the output of this board is supplied to analog-digital conversion (ADC) pins

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of the MCU. Although the related values are defined as current and voltages of solar panels and wind turbine, there are several measurements such as battery voltage, temperature, charge values etc. can be done by using the data acquisition card designed. Therefore, all the ADC ports of 18F4450 MCU are configured according to USB communication for possible future measurements. The obtained analog measurement results are processed in the MCU after digital conversion steps and the flowchart introduced in Fig. 8 is run on MCU. The user interface of monitoring tool is shown in Fig.10. The monitoring tool of the hybrid system is developed with Visual C#.Net software development kit of .Net Studio. The acquired values are processed and are transmitted by the MCU to PC


over USB port. The usb control routine of the developed tool writes the received data to a database (DB) file in each acquiring interval. The second step of monitoring process is gathering the related dataset from the DB file. The measured values are obtained from DB synchronously and are written in the related textboxes that are located on the lower left-hand side of user interface. There a calibrating conversion is applied in interface software that the measured real values are instantly seen in textboxes. The instantly measured values are also visualized in separate line graphs for each parameter where the line graphs are drawn by adding instant values and connecting line dots

(b)

(a) Fig. 9. Hardware of the monitoring system; a) general view, b) boards.

Fig. 10. The screenshot of monitoring tool

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together. Although the monitoring interface display real time measurement results on textboxes and current or voltage graphs, it is also possible to reach DB file to analyze history of the hybrid RES system. V.

CONCLUSIONS

In this paper a parameter monitoring tool that is designed to observe voltage and current values of a hybrid RES system with real time tracking property is introduced. The energy generation system is built with a wind turbine and solar panels arrays where the generated energy is coupled over a dc-bus and then is supplied to battery pack that consist eight gel batteries with 12V/100A current and voltage rates. The monitoring system can be considered in two parts as hardware and software. The hardware part is built with sensing, voltage attenuator, measurement and calibration, and MCU control boards. All the designed boards perform the measurement and communication operation between hybrid RES and PC in the mentioned queue. The monitoring interface is coded with Visual C# of .Net framework. The developed tool manages the USB communication between 18F4450 MCU and provides mutual control operation. The measured values are stored in a permanent database and user interface generates the graphics by gathering datasets from DB file where each measurement is stored in a column. Although the monitoring interface uses real time measurement results to prepare the current and voltage graphics, it is also possible to reach DB file to analyze history of the hybrid RES system. In future studies, it is aimed to develop the monitoring tool by adding user controls that provide analysis features by generating daily, weekly or monthly graphics according to requested selection. The developed tool can be adapted to a web site owing to deploying properties of .Net studio ACKNOWLEDGMENT This study is a part of a scientific research project that is funded by Scientific Research Division (NEUBAP) of

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Nevsehir University with ref. No. 2012/13. Ersan Kabalci thanks to NEUBAP Division for the support. REFERENCES [1]

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