DEVELOPMENT OF AN INTEGRATED DATA ACQUISITION SYSTEM FOR SPV SYSTEM MONITORING USING LabVIEW Rajkumar Viral1*, Tarannum Bahar2
1
Studnet Member IEEE, AHEC, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand247667, India, 2 Assistant Professor, Vira College of Eng. Bijnor U.P.-246701, India * Email:
[email protected], M: 9897675190
Abstract The increasing demand and application of Renewable Energy Systems (RESs) during the last three decades resulted in the installation of many RES power systems such as small hydro, wind, solar- photovoltaic (SPV), biomass based etc. SPV is one of the renewable energy source, which grown from the past rapidly and used to electrify isolated and remotely distributed rural communities like in India. The widespread application of these RESs requires use of data acquisition in order to collect data, regarding the installed system operation monitoring and performance evaluation purposes. In this paper, the development of a computer based data acquisition system for remote monitoring of a SPV system is presented. The proposed software tool integrates several types of instruments into a single system which is able to offer dynamic measurements all data sources and compare simulation results with monitored data in real-time. The collected data are first conditioned using precision electronic circuits and then interfaced to a personal Computer (PC)/Laptop using data-acquisition modules. Comprehensive monitoring and analyzing of SPV systems play a very important role. The National Instrument (NI) LabVIEW program is used to further process, display and store the collected data in the PC/laptop. The modern feature of this data acquisition is to access the system at remote location using internet. The proposed architecture permits the rapid system development and has the advantage of flexibility in the case of changes, while it can be easily extended for monitoring I/O (Input/output) of the remotely located SPV systems’ operation and its performance evaluation easily. This may be also led to help in control the SPV system remotely/wirelessly.
Keywords: RESs; SPV systems; Monitoring; Simulation 1. Introduction The research interests in renewable energy, especially the solar energy, are continuously increasing because of the rising price of the traditional energy resources and the serious environmental pollution. The SPV market has been growing spectacularly over the last years and is forecast confirm this trend in the coming years. The reduction of PV generation costs and the implantation of grid connected PV systems are mainly responsible of this trend. In context to above, using SPV systems is an attractive and significant alternative. SPV are relatively simple machines with no special designing and are readily available in most developing countries. Besides, their installation, commissioning and maintenance are easy and cheap [1-2]. SPV stations is one of the renewable energy source, which grown from the past rapidly and used to electrify isolated and remotely distributed rural communities like in India. Their monitoring and maintenance is the most concern and important issue when these systems are located in very remote areas. With the rapid developments of internet and computer technologies, accessing and operating of real time applications is becoming reality. Many modern data acquisition system have developed and available now to evaluate the parameter and performance of such kind of systems (PV generator/module, battery, inverter/charge regulator etc.), when they are in operation. In the line of above a data-acquisition system used for monitoring the performance of both photovoltaic battery charging [2] and water-pumping systems [3] is shown in Fig.1 (a). A different approach has been proposed in [4], as shown in Fig. 1(b). A commercial data-logging unit has been used to measure a set of meteorological and operational parameters of a hybrid photovoltaic–diesel system. The collected data are transmitted to a PC through an RS-232 serial interface, where they are processed using the LabVIEW data acquisition software. One another approach is in [5], a computer-based data-acquisition system for monitoring both meteorological data and renewable energy sources system operational parameters is proposed. A block diagram of the proposed system is shown in Fig.
2. But in order to monitor and easily evaluation of real time performance of the SPV system it is desirable to develop an integrated data acquisition system with a user friendly control and operation of it.
Fig. 1(a) A microcontroller-based Data-acquisition architectures for RES
Fig. 1(b) Data-acquisition architectures for RES systems of a data logging unit connected to a PC.
Fig. 2 Data-acquisition architectures for computer based RES systems
In this paper, a more accessible and realistic way of development of a computer-based data-acquisition system for monitoring of SPV unit is presented. The proposed system consists of a set of transducers (sensors) for measuring both non-electrical and electrical parameters. A block diagram of the proposed system is shown in Fig.3. The sensor signals are first filtered and amplified using precision electronic circuits and then are interfaced to a PC, through the PCI bus, using a commercially available data-acquisition card. The collected data are further processed, displayed on the monitor and stored in the disk using the National Instruments LabVIEW software. Also, the LabVIEW provides an easy-to-use graphical environment that permits the system operators to process easily the collected data, using complex data-processing algorithms, without detailed knowledge of the data-acquisition system design [6]. This paper is set out as follows, a brief description of SPV. The second section of paper is emphasis on the SPV background. The third section acquaints the readers with the SPV experimental setup. Fourth section familiar with data collection and interfacing process. Section five focuses on data representation in LabVIEW. Sixth section shows the experimental results and discussion. The last section summarizes the conclusion of the paper.
Fig. 3 Block diagram of the proposed system
2. Solar Photovoltaic System Photovoltaic systems use solar panels to convert sunlight into electricity. A system is made up of one or more photovoltaic panels, a DC/AC power converter (also known as an inverter), a racking system that holds the solar panels, electrical interconnections, and mounting for other components. Optionally it may include a maximum power point tracker (MPPT), battery system and charger, solar tracker, energy management software, solar concentrators or other equipment. A small PV system may provide energy to a single consumer, or to an isolated device like a lamp or a weather instrument. Large grid-connected PV systems can provide the energy needed by many customers. The electricity generated can be either stored, used directly (island/standalone plant), or fed into a large electricity grid powered by central generation plants (grid-connected/grid-tied plant), or combined with one or many domestic electricity generators to feed into a small grid (hybrid plant) [7-8]. Systems are generally designed in order to ensure the highest energy yield for a given investment. The solar PV market has been growing spectacularly over the last years and is forecast confirm this trend in the coming years. The reduction of PV generation costs and the implantation of grid connected and off-grid PV systems are mainly responsible of this trend. As a result, manufacturers of PV modules are offering new powerful PV modules, incorporating solar cells of bigger size, specially designed for integration in buildings or forming part of tracking systems. These grid connected PV systems are frequently mounted on building roofs, facades, or urban environment, where partial shading can be frequent.
3. SPV Test Setup A complete test rig of a SPV system is installed in renewable energy technology park at Alternate Hydro Energy Centre (AHEC), Indian Institute of Technology, Roorkee, India as shown in Fig.4. The proposed method of monitoring, modelling and simulation of PV systems has been applied to an off-grid connected PV system. The PV system is formed by 24 PV modules (1.296 kWp, at 1000 w/m2) divided in two arrays of 0.648 kWp each one. Each array is formed by three parallel strings of 4 PV modules in series. Each array is connected to a single phase inverter of 1.0 kW. Each module consists of 36 crystal silicon cell of 100 cm2 and produce 0.5V DC and almost 3A under full sunlight. The actual test setup picture of various instrument used are shown in Fig. 4.
OUTDOR SPV ARRAY AT RET PARK
PYRANOMETER
MONITORING INSTURMENTS IN LAB
ELECTRICAL LOAD
NI USB 6212 DAQ CARD
DAQ CONNECTION
Fig. 4 The actual test setup pictures of various instruments
3.1 Parameters Measuring The proposed data acquisition system under consideration used to measure the following two types of parameters namely: (i) Non-electrical Parameters Irradiance Temperature (ii) Electrical Parameters
Current and voltages at DC side of the system Current and voltages at AC side of the system
3.2 The Transducers/sensors and Interface Circuits Above mentioned parameter required the various type of transducers/sensors which convert the primary non electrical quantities into electrical which can be used for further processing to interface circuit. The transducers/sensors are: (i) Pyranometer [9] The MP-200 has a separate sensor while the handheld meter displays and stores measurements. The sensor housing design features a fully potted, domed-shaped head making the sensor fully weather proof and selfcleaning. Total shortwave radiation is an important component in determining evapo-transipration rates, energy balance, net radiation as well as monitoring solar power panels. Working completely passive, using a thermopile sensor, generates a small output voltage proportional to this flux. (ii) Temperature measurement [10] Using non-contact infrared temperature gun are used for bearing temperature measurement. (iii) CLSM-50 closed loop Hall effect current sensors (Idc) and dual operational amplifier LM1458N (Iac). (iv) Agilent 34972A [11] Acquisition systems have a built-in 6.5 digit multimeter, temperature, ammeter and voltmeter AC/ DC, resistance and frequency. Housing allows you to install up to three additional modules. Signal exceeding the threshold HI / LO and have built-in interfaces: GPIB and RS-232 (34970A) USB and LAN (34972A) Built-in web graphical user interface allows you to easily manage your device from a web browser (34972A only). The interfacing circuit and position of all transducers/sensors shown in Fig.5. All these modules are connected to the PC by means of USB port from NI USB 6212 DAQ card [12-14].
Fig. 5 Block diagram of interfacing circuit and position of various transducer/sensors
4
Data Collection and Processing Interfaces
As in Fig. 5, the data received by instruments (sensors) is to be transferred to NI USB-6212. The NI USB-6212, M Series is a low-cost multifunction DAQ board optimized for cost-sensitive applications, all the data is communicated to this specific DAQ module through 16 analog input channels as shown in Fig. 5. The NI USB-6212 series is a family of network data acquisition providing analog I/O, digital I/O (input/output), timer/counter and
other functions. Also consider the high-speed M Series devices for 5X faster sampling rates or the high-accuracy M Series devices for 4X resolution and superior measurement accuracy [15 &16].
4.1 Specification of NI PCI 6229 [11 &16] Analog Input Channels 16 Sample Rate 400 kS/s Max Voltage Range -10V, 10V Minimum Voltage Rang -200mV, 200mV Analog Output Channels 2 Max O/P Voltage 10 V Digital I/O Bidirectional Channels 32 Counter/Timers 2 Resolution 16bit Power Requirement 4.5-5.25V (No external Power, in configured state via USB Port) All transducers output connected to the analog input of NI 6212 card between A0-A15 (as shown in Fig.5. The output of this card transferred to the PC by USB port. This can be read further by LabVIEW software.
5
Data Representation
The data-acquisition card is controlled by a properly developed interface, using the LabVIEW software, running on the PC. It consists of two parts first is a graphical environment with components such as displays, buttons and charts in order to provide a convenient-to-use environment for the system operator called front panel, and second is the program code, which is in block-diagram format and consists of built-in virtual instruments (VIs) performing functions such as analog channel sampling, mathematical operations, file management etc. The LabVIEW 8.6 software runs under the Windows 95/98/NT/2000 operating system or earlier than [15-16]. It contains Dials, Graphs etc. to display the parameters. LabVIEW is programmed to sense change in parameters every second and according to that display on the screen. The screen contains block diagram for each parameter measurement, which can be seen, after stop the program, it shows the virtual form of cable connection and the values of data at each stage of transfer. The greater reliability of LabVIEW program is that it can be access through internet using its web publishing tool in tool menu. This tool allows modifying the look of the document in the web browser. Title, Header, and Footer text and the previewing the document in web browser, then click save to disk. This is saved to the .html file to the www directory. Name and save the file then click ok. This will bring up another window giving the URL name of the document for putting in the web browser. The sample code block diagram (VI) and the final user’s monitoring screen developed in LabVIEW program is illustrated in Fig. 6 & 7 respectively. The front panels in Fig.7 also show the real time VI characteristics of SPV system, non-electrical (irradiance, module temperature, cell surface used) and electrical parameters (Isc, Voc, Rs, Rsh, µ, output power). It also shows the measured data on right hand side panel.
Fig. 6 VI developed of the proposed SPV system
Fig. 7 LabVIEW front panel of the proposed SPV system
6
Experimental Results & Discussion
The PAT generator unit set monitored through LabVIEW software and manually. The numerical values of various parameters are given in the Table 1. Table 1 shows the Electrical parameter reading measured manually and using software simulation on PC/laptop. The front panel also show the real time VI characteristics, module temperature, which could easily help to evaluation of performance of SPV system. The results clearly show that this system is given accurate and correct results. It is also show deviation in LabVIEW reading (PC Reading) and Meter Readings (M.R). All these parameters extracted for 12 PV module at 762 W/m2 of irradiance and 26.2 oC of temperature. S.No . 1 2 3 4 5
7
Isc (A) M.R* 5.07 5.94 6.02 6.01 5.95
PC* 5.01 5.89 5.95 5.91 5.90
Voc (V) M.R 20.4 20.0 18.95 19.59 19.99
PC 20.0 19.88 18.59 19.52 19.89
Table 1 Electrical parameters monitored Iph (A) Io (A) M.R 5.10 4.88 5.01 5.0 4.79
PC 5.00 4.80 4.95 4.97 4.76
M.R 1.9x10-8 1.95x10-7 1.80x10-6 1.8x10-7 1.91x10-9
Im (A)
Vm (V)
PC M.R PC M.R PC 1.89x10-8 4.53 4.6 16.31 60 1.92x10-8 4.28 4.21 15.56 15.51 1.76x10-6 4.01 4.00 16.02 15.93 1.81x10-7 5.02 5.00 16.00 16.01 1.90x10-9 5.25 5.21 16.08 16.01 (M.R*: Meter Reading, PC : LabVIEW Reading)
Conclusions
This works presents an integral LabVIEW platform of monitoring, modelling and simulation of off-grid connected PV systems. In the same platform, we propose the modelling of the PV module identified with outdoor measurements of I–V curves in order to extract the main PV module parameters. The PV module modelling and extraction parameters procedure has been successfully validated experimentally. The development of a computer based DAQ for SPV system generator set is analyzed in this paper. The proposed method is based on precision electronic circuits and an easy-to-use graphical environment, based on the LabVIEW program, for processing, displaying and storing the collected data. The system operator can easily process of the measured parameters and evaluate the performance (efficiency) of the system directly from the user front panel of LabVIEW in very short time. The system can be monitor remotely by using internet and web publishing tool of LabVIEW. It is helpful in monitors the SPV based power plants which is generally located at remote and isolate places. This system can be extended in future for control the I/O remotely of SPV by some hardware modification.
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