Solar Power Inverters, Analysis And Test Evaluation

Project and Seminar Material For Electrical Electronics Engineering EEE

Abstract

Solar energy is a major renewable energy source in Nigeria, which is the energy obtained from the radiation of the sun. It is mainly used to convert the DC electrical energy from solar PV modules into AC quantity. One of such major renewable power sources in use is solar energy. This paper presents a platform for carrying out standard basic tests and analysis on solar inverters for electrical/electronic engineering students/instructors, as well as providing a foundation for conducting standard comparison between inverter brands. The aim of this study is to provide a means for the determination of the best type of batteries required for a particular solar power system installation. The tests were carried out within a four week period. Within a five-week period, various tests were conducted on two invertector brands, blue gate and luminous. The brands tested were the famous blue gate inversions and a luminous inversion. This discovery will allow a better choice of selection of invertors for students who wish to major in the field of solar power systems installation in future times. This study will have no understandable meaning or importance without it being able to present solutions to some of the problems posed while embarking in a solar power installation project.

Chapter One

Introduction

The quest to satisfy our need for stable power supply in Nigeria has driven most Nigerians into an ardent search for alternative renewable power sources. One of such major renewable power source in use is solar energy, which is energy obtained from the radiation of the sun.

To obtain electrical power from the sun, four key components are required to effectively and efficiently convert the sun’s radiation energy.

These four key components include:

A solar energy-conversion system (Solar PV modules or array)
A regulation system (Charge controllers)
Electrical energy storage media (Batteries)
DC-AC conversion system (Inverters)

Fig 1.1: Simple diagram of a house hold Solar Power System [85]

Fig. 1.1 above gives the diagrammatic description of a solar power system. As can be seen from the diagram, radiant energy from the sun striking the solar panels is converted into DC voltage which is fed into a battery through a charge controller. The electrical energy stored in the battery is then converted from DC to AC, and stepped up to the voltage level required for the operation of house hold electrical equipment.

It is important to note that to efficiently and effectively convert the DC electrical energy from solar PV modules into AC quantity, an inverter must be incorporated into the system. The area of contention, as regards to this project report is in the area of selection of the most efficient and cheap solar inverter. Knowing how efficient an inverter will be can only be determined through usage and/or testing of the inverter in question, and further analyzing the results obtained, in order to compare them with that of an ideal inverter. This whole idea gave birth to the topic of this project “Solar power inverters, analysis and test Evaluation”

It is our belief that an inverter whose characteristics is close to that of an ideal inverter can be regarded as a good inverter, while that whose characteristics is far from an ideal inverter can be regarded as inefficient.

As mentioned before electricity crises is a major problem in the present era. This problem is even more critical for a densely populated poverty corrupted developing third world country like Nigeria. A lot of people live here without the basic facility of electricity. Daily, electricity crises and price is increasing whereas no other solution is left for us without using the solar power or diesel turbine to generate electricity in remote areas which seems to be very expensive to run. Again, not only do we face electricity crisis but also, the cost of gas and other natural resources like fuel, diesel , petroleum etc. is on the increase, beyond the reach of the general populace. To this effect, a system capable of not only reducing the electricity crisis but also the need for petroleum or other natural resources used in energy generation is therefore the desired choice in Nigeria today.

Presently, the demand for solar power generating system is on the increase, as the world today is seeking better sources of electricity lees capable of causing damage to the environment.

1.1 Statement of Problem

This report will have no understandable meaning or importance without it being able to present solutions to some of the problems posed while embarking in a solar power installation project, as well as provide answers to some of the questions commonly asked by electrical engineering students when faced with solar power system installation. To this effect, the problems/questions listed below follows.

How do we determine the best type of inverters from a selection provided in today’s market?
How do we determine the best type of batteries required for a particular solar power system installation?
What process(es) is/are required for the determination of the actual operating characteristics/properties of an inverter, when given an inverter whose operating characteristics are not given?
How do we carry out a troubleshooting operation for a faulty inverter?
How do we know the amount of distortion introduced into the output of an inverter by the presence of harmonics?

1.2 Aims and Objectives of this Study

The aim of this study is to provide a platform for carrying out standard basic tests and analysis on solar inverters for electrical/electronic engineering students/instructors, as well as provide a foundation for carrying out standard comparison between inverter brands.

The objectives of this study thus follow:

To provide a platform for the selection of the best type of inverters from an available market selection.
To provide a means for the determination of the best type of batteries required for a particular solar power system installation
To provide a standard list(s) of tests required for determination of the basic operating characteristics of solar inverters.
To provide an encyclopedia of information on solar power system for students who wish to major in the field of solar power system installation
To familiarize electrical/electronics engineering students with the solar power installation and harvesting process.
Study methodology

Within a four week period, various tests were carried out on two inverter brands. The results obtained from these tests were recorded on a record sheet in a tabular form, graphs were plotted with the information recorded, and comparisons were made based on the graphs obtained.

The brands of inverters tested were the famous blue gate inverters and luminous inverter technologies. The tests carried out were repeated severally to obtain correct values. Basic tests carried out include:

Variable load test
Constant load over time
Idle test
Night time power consumption

Generally, all tests were grouped into:

Test for input characteristics
Test for output characteristics
Protection test and other special tests.

The wave form of both inverters were also observed on an oscilloscope, and comparisons were made and recorded in chapter five (5) of this report. The harmonic distortions were observed but not measured.

1.3 Limitations of the Study

Within the course of this project, certain problems/constraints were encountered. Some of these problems/constraints encountered marginalized the area under study while others prevented the complete carrying out of certain tests/test procedures. Some of these problems include:

Poor state of equipment; some analogue measuring equipment like the high range ammeter available was improperly damped, making it almost impossible to read instantaneous values of current.

There was a shortage in the availability of high range measuring equipment at the school lab. This restricted tests carried out to lower values. Certain tests had to be attenuated or completely stopped when the values obtained exceeded the deflection of analogue meters, or the range of digital meters.

Unavailability of certain measuring equipment like the THD analyzer used in the measurement of harmonic distortion. Computer programs like the PV array simulator, required to carry out MPPT performance test was also not available.

As a result of shortage in certain measuring equipment, the data collected were from various measuring instrument ( analogue, digital), leading to a non-uniform measurement

Unavailability of standard connecting cables

The duration for the study, when compared to the volume of work required for completely carrying out the project was limited.

We also had inadequate financing as at the instant it was required.

Chapter Five

5.0 Conclusion and Recommendation

5.1 Conclusion

As a result of carrying out the tests listed in chapter three of this report, one can testify of a greater understanding of the behavior of inverters and solar power systems while in operation. Although a lot of problems where encountered within the course of this project work, it is a thing of joy to know that a platform has been laid for the complete success of future research in this area of study. With the tests carried out on the two inverters, the weak points in their operation were discovered. This discovery will allow for a better choice of selection of inverters while carrying out solar power system installation in future times.

5.2 Recommendation

As said before in introductory part of this report, certain problems were encountered within the course of carrying out this experiment. It will be essential at this point to therefore, make certain recommendations towards annulling the presence of these presently faced problems in future researches. Again, some disturbing discoveries were observed in the operation of the inverters while carrying out certain test. Recommendations will also have to be made towards ensuring that these discoveries are taken care of.

To allow full understanding of the message being passed in this section, the recommendations made will be discussed under the following sub-headings

Recommendations made to the Department of Electrical/Electronic Engineering, Ambrose Alli University
Recommendations made to the local and foreign producers of inverter.
Recommendations made to the Nigerian government
Recommendations made to the users of solar inverters world over.
Recommendations made to the installers of solar power equipment in Nigeria.
Recommendations made to the management of Ambrose Alli University

i. Recommendations made to the Department of Electrical/Electronic Engineering, Ambrose Alli University

One of the major problems faced while carrying out this project work was the shortage of standard measuring equipment as well as the unavailability of certain test equipment like the THD analyzer, and the PV simulation software. It is therefore a necessity that more standard measuring equipment be purchased for laboratory work. Also the need to purchase high voltage and current measuring equipment should be met as certain test carried out within the cause of this project work were cut short due to the inability of the available measuring device to measure beyond certain values. New equipment like the THD analyzer should be purchased for laboratory work.
The available oscilloscope in the lab should also be upgraded to synchronize with computer systems so as to allow easy retrieval of the information being analyzed on the oscilloscope screen. Modern day oscilloscopes should also be bought to replace the non-functional ones in the lab

ii. Recommendations made to the local and foreign producers of inverter.

The foreign producers of inverters should provide more safety information on the use of inverters to their customers. Furthermore a standard inverter output characteristic should be agreed upon by all inverter producers.
The local producers of inverters in Nigeria should be made to run standard health and safety tests on the inverters they produce to ensure the safety of the users of these inverter. More protective systems should also be incorporated into locally made inverters inorder to prevent the occurrence of damage to the internal circuitry of the inverters, as have been the case in recent times.

Inverter producers should also learn to provide genuine information regarding the functional characteristics their products. Again, grid connected inverters must be provided with anti-Islanding circuits.

iii. Recommendations made to the Nigerian government

The Nigerian government should a regulatory council to govern the standard of inverters and other electronic equipment imported into the country.

Local producers of inverters should also be encouraged through provision of soft loans and standard safety test equipment for the production and proper testing of locally made inverters. If possible technocrats should be employed from foreign nations like Japan to teach the local inverter producers how best to raise the standard of their produced inverters. Furthermore the importation of inverters into Nigeria should be stopped to encourage the growth infant inverter producing industries within Nigeria.

Northern Nigeria has adequate sun shine, enough to provide electricity to over 40% of the North. The government of Nigeria should therefore provide more funds for further and deeper research into solar power farms to ascertain the viability of using solar power in the elimination of Nigeria power crises.

iv. Recommendations made to the users of solar inverters world over.

One of the major reasons for the malfunctioning of electrical/electronic equipment is misuse on the part of the equipment owners and users. As regards inverters these two major recommendations is of importance to users and owners.

Inverters must not be allowed to undergo excessive continual overloading as this will lead to gradual damage of some of the internal circuitry of the inverter. Users should also be aware of the fact that the KVA rating of an inverter is not the actual amount of power that can be delivered by such inverter, and a such should not try to load any inverter up to its stated KVA rating. Inverters should not be turned ON always on overload.
Inverters should not be forcefully switched on after being turned off by its low battery protective circuit. This is one of the major cause of damage to inverters installed in residential and office environment. Once an inverter turns off on low battery, leave it OFF and charge its batteries before turning it ON again.

v. Recommendations made to the installers of solar power equipment in Nigeria.

Installers of solar power systems are themselves one of the causes of failure of any solar power system. This is so because they are responsible for providing the information on the choice of equipment rating to clients or users of solar power system. A situation were wrong information as regards installation capacity is provided may cause overloading of the inverter to be installed. The following recommendations are thus required to be met by solar power equipment installers.

Installers of solar power equipment should be made to possess a qualification in the field of Electrical power systems, before being allowed to dabble into the installation of solar power equipment.
Every installer should be made have a working knowledge of solar inverters before being allowed to practice.
Evaluation should be carried out on the load to be powered before making a choice on the inverter to use for any installation.

vi. Recommendations made to the management of Ambrose Alli University

The school management should provide finance to the department of Electrical engineering towards carrying out deep research into solar power systems. A production factory where inventive students can mass produce their designs for sales should also be built in the faculty of Engineering. This will go a long in encouraging students to work hard as well as provide finance for both the school and students. Most project designs done in previous years have good market potential in Nigeria but the absence of a production factory to mass produce and sell off these designs remains a hindrance.

The management of Ambrose Alli University Ekpoma, should embrace the use of solar power in cutting down the amount of money spent in electricity bill payment per annum. Since all official hours are within the day, solar power will be a veritable choice to power office electrical equipment within the day.