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Monday, 30 January 2017

Role of Simulation Softwares in Solar PV plant Design and Operation

The performance of a Solar PV plant depends on the solar irradiation, the optimum tilt angle, ambient temperature, design parameters, quality of modules, efficiency of inverters etc. The output power of solar PV module is directly proportional to the solar irradiation.

Earlier the expected generation output, losses in cables & equipments, voltage drop, lower and upper range of array voltage etc. were manually calculated. Now-a-days this tendency is fast being replaced by advanced simulation software, particularly in the case of solar PV plants with significant capacity.

Function of Simulation Softwares in plant Design and Operation:

Softwares are used as essential tools in the design, construction, operation and maintenance of Solar PV plants. They help to produce solar PV generation assessments, and site-specific production forecast accounting the location latitude and longitude, weather condition, shadow effect etc. These softwares lend a hand to optimize design configurations and system layouts, test the system performance. 

Economic evaluation and payback period calculation are also facilitated by these softwares. They also make possible the integration of PV plant output to the Utility grid, monitoring and control of the plant health, thus enhancing the operation of the PV plant.

Popular softwares:

There are several softwares available for assisting the solar PV system designing. The popular are:

1.       PVSYST
2.       PVSOL
3.       Solar Advisor Model (SAM)
4.       SMA off-grid Configurator
5.       Solar Pro
6.       PV Design Pro
7.       HELIOS 3D

PVSYST is one of the oldest and trusted PV designing software developed by the University of Geneva. The software offers a wide range of features, a few are –

1.Complete designing of off-grid and grid connected solar PV system.
2.Complete data base of solar modules and inverters.
3.Meteorological data of a large number of stations and sites across the world. Data of new sites can also be imported.
4.Access to PVGIS and NASA database for import of irradiation data.
5.Enables economic evaluation and payback period.
6.Predicts and asses the module behaviour under varying irradiation, ambient temperature and shading scenarios.

PVSYST software has two modes:
1.       Preliminary mode, and
2.       Project design mode.

In the preliminary mode one can get the approximate value of power generation. Project design mode allows user defined values for inverter efficiency, losses and shading effect. The results of these softwares are in the form of report, tables and graphs. The software is available in a trial version with one month access period. Cost of the software depends on its version and the number of design to be carried out per month.     

 Free Softwares:

Some free to download softwares such as PVGIS Estimation Utility, SMA Sunny Design etc are also available which can be used in the design of solar PV system.

PVGIS Estimation Utility is one such software which is freely available. With the help of this software one can calculate the output of a proposed solar PV plant, optimize the design and can have a fair idea about how the PV system is going to perform when completed.

Another free software is “SMA Sunny Design” by renowned solar inverter manufacturer SMA. The software generates detailed reports in “pdf” format of the proposed solar PV plant. The typical input required are the number and type of PV module to be used, location details, roof pitch etc. The software is able to compare the performance of PV panels of different types, makes and models. Although the software has the database of most of the solar PV panels, but one can have the option of feeding his/her own PV module details.

How the Software help out in plant Operation:

After the successful commissioning of a Solar PV plant, the next important activities are monitoring and operation & maintenance of the plant. There are softwares that help in carrying out these works also. The software can indentify under-performing plant and arrays, and thus help in increasing the power production. Incoming data from the PV modules, instruments to monitor the ambient, inverters, transformers and grid interfacing equipments are analyzed. Smart and advanced sensors and data loggers collect this information that affect the PV plant’s performance, and allow the software to create real time performance models. Variances are detected, and notifications and alarm messages are given to the concerned agency/ person.

Thus these softwares can create custom analytics, alerts, contracts and reports. They also helps in streamlining the operation & maintenance activities, and hence reduces Mean Time to Repair (MTTR). They also help in forecasting the power generation of the PV plant based on the weather forecast.  

 One such software is the Qantum Solar Monitoring and O&M software.

Friday, 27 January 2017

Digital Multi-Meters: A very handy tool for Electrical Engineers

An electrical engineer and electrician must be familiar with a variety of test and measurement instruments. They need to know how to use these instruments in a safe and proper way under different working conditions. It is important to use the right tools and instruments when working with electricity. Appropriate equipments can make a hard task easy and at the same time wrong selection can make an easy job difficult and dangerous.

This article looks at the most common type of meter available with an electrical engineer or electrician; i.e. the Multi-meter. 

Another versatile and handy instrument for an electrical engineer, particularly in the Solar PV field, is the digital clamp meter

Multi-meters are hand-held instruments designed to measure more than one electrical value; for example DC and AC voltages, DC and AC current, resistance etc. They are also used to check the continuity of conductors or to check the diode. Figure 1 shows the icon of some of the electrical quantities measured by a multi-meter.

Fig.1: Icon of some of the electrical quantities measured by a multi-meter.

In other words, a multi-meter is a measuring instrument that combines an ammeter, a voltmeter and an ohmmeter to measure the current, voltage and resistance in a circuit; means no need to carry different meters for measuring different values.

Digital Multi-meter:

Both analog and digital multi-meters are available, but the digital version has superseded the analog one. Digital Multi-meters (DMM) has a digital display to show the measured values, a dial or selector switch to change the mode of the meter, and connecting terminals. Figure 2 shows a low cost commonly available DMM.

Fig. 2: Low cost commonly available DMM.

Accessories such as a pair of red and black probes, is also provided with the meters. The black probe is always considered as the negative probe and is connected to the common terminal. Figure 3 shows the probe provided with the DMM.

Fig. 3: Probe provided with the DMM.

System with Harmonics:

When harmonics is present in the system, only true RMS meters can provide accurate measurement   of AC values. Harmonics are frequencies that are multiples of the fundamental frequency (50 Hz in India) and can cause distortion of basic AC waveform. The common loads which causes harmonics in the system are computers, fluorescent luminaires with electronic ballast, inverters etc. These electrical loads are also called Non-linear loads as their impedance are not constant.

Working of Digital Multi-Meter:

The basic circuit of a Digital Multi-Meter is always a DC voltmeter. The AC quantity is rectified into DC with the help of rectifiers and filters. All the quantities are digitised using an Analog to Digital Converter (ADC) and displayed in the digital form on the display.

Figure 4 shows the internal circuit of a commonly available Digital Multi-Meter.
Fig.4: Internal circuit of a commonly available Digital Multi-Meter.

Advantages of Digital Multi-Meter:

Digital Multi-Meters have the following advantages over analog:
1.       Cheap and compact,
2.       Accuracy is very high,
3.       No loading effect,
4.       Reading of values is much easier,
5.       Can be interfaced with external equipment,


“Always read and follow the manufacturer’s instructions that are supplied with the Multi-meter. Equipments may be damaged badly and or the user may be seriously injured if proper safety procedures and instructions are not followed.”
Safety is very important when using test and measurement instruments. Many a times, the meter is used to make the measurement while the electrical circuit is energized. Ensure to follow the regular and standard safety procedures when working on live circuits. A safe working practice is always mandatory. The following safety tips are recommended-

1.       Ensure the correct position of selector switch,
2.       Do not be alone when working on live circuits,
3.       Keep your hands dry when taking measurements,

4.  Use rubber gloves and wear shoes when taking measurements on energized circuits.