Stand-alone Photovoltaic Power Research Articles

Mission profile-based assessment of photovoltaic system reliability for Indian climatic zones

ABSTRACT Solar energy is expected to overtake wind energy as the leading renewable energy source by 2050, and therefore, accurate lifetime and reliability predictions for solar photovoltaic (PV) installations are necessary. The microinverter is a pivotal component of stand-alone PV power systems. The reliability of the microinverter depends on the mission profile of the geographical location, such as solar irradiance, ambient temperature, and wind velocity. This study developed a comprehensive reliability map for a 200Wp monocrystalline panel and a 250W microinverter based on mission profile data collected from 198 locations across India. A novel mathematical model is developed and validated using Ansys Icepak to evaluate the junction temperatures of microinverter components. The results show that the junction temperature significantly affects the reliability of PV system. In the hot and dry climatic zone of Jaisalmer, Rajasthan, the maximum MOSFET junction temperature and Mean Time Between Failure (MTBF) obtained were 63.14°C, and 27.34 years, respectively. Furthermore, in the cold and dry climatic zone of Leh, Ladakh, the junction temperature dropped to 29.74°C, increasing MOSFET’s MTBF to 49.8 years. These results prove that the reliability depends on the mission profile, and it should not be ignored in evaluating the reliability of solar PV systems.

A Novel Bidirectional DC–DC Converter with Low Stress and Low Magnitude Ripples for Stand-Alone Photovoltaic Power Systems

Photovoltaic (PV) power is one of the promising solutions to address the fast-growing electricity demand. Electricity generated from the array of solar panels is not fixed due to the continuous change in environmental conditions. Therefore, an efficient power management system is required to facilitate the consumer with an uninterruptable power supply (UPS). When the energy demand is lower than the energy generated by the PV power system, the excessive energy must be stored in batteries and, when the energy demand is higher than the energy generated by the PV system, then the stored energy in the battery must be released in order to fulfil the load demand. Therefore, a bidirectional DC–DC converter is required to store and release energy. Conventional bidirectional converters offer low gain, low power density, low efficiency, high switching stress, and high magnitude of current and voltage ripples. In this paper, a bi-directional DC–DC converter that has low stress and low ripples is proposed for the operation of Stand-alone PV power systems. The proposed converter is implemented in ORCAD/PSPICE (Oregon Computer Aided Design/Personal Computer Simulation Program with Integrated Circuit) and both the charging and discharging modes have been analyzed explicitly. The results were compared with conventional converters and were found to be satisfactory. A significant improvement in the magnitude of output voltage and current ripples has been noticed. Besides, considerable improvement in switching stress (45% reduction as compared with conventional converters) and a 16.6% reduction in the magnitude of ripples was realized.

Design of Neuro-Fuzzy Controller for Stabilization of Single Phase Stand-Alone PV Power System

For the three phase power electronic and drive applications, vector control or the synchronous reference frame (SRF) based control concept is well accepted and settled amongst the research communities. Although the SRF concept has gained popularity and appreciation in developing the three phase controllers, still the concept has not reached the same level in case of a single phase system. The work presented in this paper is mainly concerned to the design of a hybrid Artificial Neural Network and Fuzzy Logic based controller for a single phase stand-alone photo-voltaic (PV) power system. The adaptive neuro fuzzy inference system (ANFIS) controller proposed in this paper is chiefly meant for improving the transient and steady state responses; for minimizing the distorting effect of the low order load current harmonics encountered particularly in case of switching the drive based inductive loads and to help maintain the inverter output voltage constant under different loading circumstances. The result obtained through simulation work, shows the effectiveness of the proposed controller as compared with the previously established research works.

Self-sufficiency of 3-D printers: utilizing stand-alone solar photovoltaic power systems

A self-replicating rapid prototyper (RepRap) is a type of 3-D printer capable of printing many of its own components in addition to a wide assortment of products from high-value scientific or medical tools to household products and toys. There is some evidence that these printers could provide low-cost distributed manufacturing in underprivileged rural areas. For the most isolated communities without access to the electric grid, a low-cost alternative energy is needed. Solar energy can be harvested through a stand-alone photovoltaic (PV) power system specifically designed to match the needs of the RepRap. The voltage and current requirement for the printer demands the use of buck along with a bidirectional DC converters to ensure proper operation. This paper provides the design for a stand-alone PV—lithium ion battery power system with an efficient controller. Robust and agile PI controller schemes are utilized to efficiently maintain the distribution of energy through the power system. The system was defined with ordinary differential equations, simulated and tested for two operational conditions in MATLAB/Simulink. The results showed that the controller developed operates the system in a stable condition and the simulation shows steady acceptable behavior that makes this system highly suitable for hardware implementation.

A Practical performance verification of AFLC based MPPT for standalone PV power system under varying weather condi-tion

For amelioration of tracking efficiency, the Maximum power point trackers (MPPT) are very important for photovoltaic (PV) generation. For this purpose here a reformed adaptive fuzzy logic control (FLC) MPPT tracker has been presented to enhance its overall power efficiency and gives rapid transient response under changing weather conditions. For voltage regulation at load bus, the zeta buck-boost converter has been taken for its least voltage ripple. MATLAB/SIMULINK simulation environment and dSPACE DS1104 real time control board is used to test the proposed adaptive fuzzy logic controller based MPPT in variable irradiance level and ambient tempera-ture. The tracking efficiency in this presented method is analyzed in comparison with standard fuzzy logic controller (FLC) and perturb and observe (P and O) MPPT algorithms. The modified AFLC controller gives better tracking efficiency and precise response compared to conventional fuzzy logic controller and P and O MPPT algorithms. Theoretical and experimental results obtained are demonstrated for improved functioning of the system.

Design and Optimization of Standalone Photovoltaic Power System for Ethiopian Rural School Electrification

Power is one of the basic need of the Ethiopian society and organization for cooking, lighting and to run different office or other place electrical devices like TV, radio, computer, fans etc. In Ethiopia grid electrical power supply is still not supplied to rural communities or organization due to the geographical topography difficulty as well as the shortage of grid power and Ethiopia has enough potential of solar energy resource. This paper presents a renewable standalone photo voltaic power system to electrify the selected rural school which are far from grid power supply for ceiling fan, office phone, lighting, computer, printer, radio and TV consumption. Therefore, this study focused on the design and optimization of the power system components by using homer software. The solar resource of the for the school site is collected. The electrical energy demand of the selected school, number of PV modules, payback period and other corresponding components as well as the initial cost estimation of the power system components and optimization of the standalone power system is done by homer software. There are 42 solar photo voltaic modules needed for the estimation energy demand of school with the energy cost of the power generated 0.13$/kwh and cash inflow 3431.1$/year for the payback period of 6.5 years.

Techno-economic viability analysis of fixed-tilt and two axis tracking stand-alone photovoltaic power system for Indian bio-climatic classification zones

This study examines the viability analysis of fixed-tilt and two axis tracking stand-alone photovoltaic (PV) power systems for electrical power generation in bio-climatic classification zones of the northeastern (NE) states of India where many remote villages are still un-electrified. Grid extension is not possible in many zones of the NE states of India because of the mountainous terrain. Therefore, as an alternative for un-electrified remote villages, the usage of stand-alone PV power systems may mitigate the power shortage problem. Based on the simulation model, the techno-economic analysis is carried out by using 22 years' of satellite-based monthly average solar radiation and temperature data. The typical load profile is also assumed for the purpose of analysis, which replicates the electrical appliances used by the end-users. The optimal fixed-tilt and optimal tracking PV system configuration along with optimal cost of energy (COE) is also obtained. The COE is found to be 0.383–0.497 $/kWh for the fixed-tilt PV system, and the same for the tracking PV system is obtained in the range of 0.523–0.732 $/kWh. From the fixed-tilt and tracking PV system, the monthly average electrical power, monthly average excess electrical power, monthly average unmet electrical load, monthly average inverter power, battery state of charge, and battery input power over the year are detailed, analyzed, and compared. Moreover, the capacity factor obtained in the case of a fixed-tilt PV system lies within the range of 14.2%–17.7% and the same is 17.6%–22.7% for the tracking PV system. Also, the findings of this study reveal detailed information regarding techno-economic and performance analysis of fixed-tilt and tracking PV power systems, which may help policy makers or investors to develop PV technology for the NE states of India.

Feasibility Analysis and Simulation of a Stand-Alone Photovoltaic Energy System for Electricity Generation and Environmental Sustainability – Equivalent to 650VA Fuel-Powered Generator – Popularly Known as “I Pass My Neighbour”

Photovoltaic (PV) power system can be used to replace wholly 650VA generator for electricity generation for household use in Nigeria. This paper presented the feasibility analysis of load data and simulation study of a stand-alone PV power system that produced the electrical needs of a household. This study is based on designing of PV energy system for household use. The patterns of load consumption within the household were studied and suitably modeled for simulation. The simulation study indicates that energy requirements to provide electricity which is equivalent to 650VA generator for household use in Nigeria can be accomplished by 520W solar PV array, 2312 Ah nominal capacity battery, and a 1kW DC/AC inverter. This would be suitable for deployment of 100% clean energy for environmental sustainability and uninterruptable power performance in the household. The results of this research show that, with a low-power consuming appliances, it is possible to meet the entire annual electricity demand of a single household solely through a stand-alone PV energy supply. Installing solar panels by most Nigerian home can significantly reduce home reliance on government power thereby reduce the strain on the current capacity of our power generation infrastructure. A detailed design and description of the system were presented in this paper.

Development of Software for Analyzing of Solar Irradiance and Sizing of Stand-Alone PV Power Systems

An analyzing software was developed for studying the solar irradiance on the Universidad Militar Nueva Granada (UMNG) Campus, as well as for sizing a stand-alone photovoltaic (PV) system in terms of power generation and energy storage, which is intended to be part of an hybrid DC smart grid with several energy sources, including not only solar but additional renewable. This software has a two stage sequential structure: First, it let to calculate the total solar energy resource and define the average irradiance and its variability for several user-defined periods, i.e. daily, monthly, annual and even multiannual. Simultaneously, the software gives the user a graphical data variation, where irradiance in hours of bright sunlight (at Standard Test Conditions - STC: 1 kWh/m2) and variability are organized in a period range (hours, days or months). The sizing stage let to define the system architecture in terms of modules and batteries, i.e. estimate PV network and battery bank. Finally, after providing load, voltage level and autonomy, it proceeds to calculations, considering factors of safety.

A Novel Maximum Power Point Tracking Technique for Photovoltaic Module Based on Power Plane Analysis of $I$– $V$ Characteristics

A new method of tracking the maximum power point (MPP) of a photovoltaic (PV) module is presented in this paper, which exploits the effects of the inherent characteristic resistances of the PV cells. An analysis of the iv characteristics of the PV module in the iv plane revealed a possibility of predicting the MPP by finding the maximum possible power rectangle within the iv characteristic. The maximum possible power rectangle has been determined by a background online sweeping technique in the power region of the iv characteristic without disturbing the PV module. The power region in the iv characteristic can be determined by the effects of the characteristic resistances of the PV module. The results obtained through simulations and experiments have validated the proposed technique. The effectiveness of the proposed method has closely matched with the true MPP, and the successful experimental results obtained with a 100-Wp PV module indicate that the technique can be favorably implemented for stand-alone PV power systems.

A two stage successive estimation based maximum power point tracking technique for photovoltaic modules

A new method of tracking the maximum power point (MPP) of a photovoltaic (PV) module exploiting the effects of the inherent characteristic resistances of the photovoltaic cells is proposed in this paper. An analysis of the mathematical model of the IV characteristic of the PV module revealed a possibility of estimating the MPP from its characteristic parameters such as the open circuit voltage (Voc), short circuit current (Isc), series resistance (Rse) and the shunt resistance (Rsh). The first stage of estimation process, for obtaining the voltage at the MPP, was facilitated by the effects of the series and shunt resistance on the IV characteristic of the PV module and the second stage of estimation process was facilitated by the combined process of the first stage of estimation and the condition for extracting the maximum power from the mathematical model of the pv characteristic of the PV module. The estimated voltage at the MPP in the second stage of estimation was found very close to the true MPP. The effectiveness of tracking the MPP with the proposed method has closely matched with the true MPP. This was validated by the results obtained through simulations and experiments. An analysis of the effects of degradation on the performance of the proposed technique showed that the performance was excellent during the first few years and with the update of characteristic resistances in the proposed algorithm the performance was found to be almost invariant. The successful experimental results obtained with a 100Wp PV module indicate that the technique can be favourably implemented for standalone PV power systems.

Assessment of electricity generation by wind power in nine costal sites in Malaysia

In this article, the wind power potential in Malaysia is examined. Hourly wind speed data for nine sites in Malaysia are used to optimally design wind power systems for remote housing electrification. These nine sites are Bintulu, Kota Kinabalu, Kuala Terengganu, Kuching, Kudat, Mersing, Sandakan, Tawau and Pulau Langkawi. The designed wind power systems are supposed to supply hourly load demand 6.13 kWh/day, 0.52 kW peak with 1% loss of load probability. The unit cost of the energy produced by each system is calculated and compared to the unit cost of the energy produced by a standalone photovoltaic (PV) power systems and a diesel generator power systems. The results show that the average unit cost of the energy produced by a wind power system in Malaysia is 1.6–7.29 USD/kWh while it is 0.35–0.5 USD/kWh and 0.27–0.30 USD/kWh for PV power system and diesel generator power system, respectively. Based on this, the use of wind power systems as standalone systems is not recommended for the selected sites.

Design and Hardware Implementation of a Versatile Photovoltaic Power Generating System

This paper presents a novel standalone photovoltaic (PV) power generating system. PV based power generating units performing the direct conversion of solar energy into electric energy constitute a major area of renewable energy based power generating systems. In practice, PV based power systems can be used to exploit the solar energy in almost all kinds of industrial and residential applications; however, designing a PV system depends on a variety of factors, such as, geographical location, solar irradiation, system configurations, operating modes and most importantly the load requirements. In this paper, a versatile standalone PV power system equipped with a battery energy storage unit is designed for a variety of small to medium power applications. To achieve a cost-effective design, both buck and buck-boost dc to dc converters are integrated to facilitate the maximum power point tracking (MPPT), battery charging/discharging and load voltage regulation functions. The details concerning the design concept of the proposed system and the related circuit operating theory are firstly addressed and followed by a set of practical tests on a dspic4001 controlled hardware prototype. Typical measured results are presented to demonstrate the feasibility and effectiveness of the proposed system

Design and Implementation of a Digitally Controlled Photovoltaic System Using Series Connected Buck Converters

In PV (photovoltaic) power systems, a MPPT (maximum power point tracking) algorithm is vital in increasing their efficiency. But it is also vital to take into account the non ideal conditions resulting from complex physical environments in such PV power systems. To minimize the degradation of performances caused by these conditions, and therefore adding reliability and robustness, this paper presents an implementation of a digitally controlled system using a topology based on series connected DC-DC buck converters for a stand-alone PV power system applications, operating with local and autonomous controls, to track the maximum power points of PV modules in non ideal conditions. Simulations are carried out by using C-MEX S-functions under MATLAB-SIMULINK environment. A PV system of 1.44 kWc is described and simulation results are presented.

Fundamental-Frequency-Modulated Six-Level Diode-Clamped Multilevel Inverter for Three-Phase Stand-Alone Photovoltaic System

This paper presents a fundamental-frequency-modulated diode-clamped multilevel inverter (DCMLI) scheme for a three-phase stand-alone photovoltaic (PV) system. The system consists of five series-connected PV modules, a six-level DCMLI generating fundamental-modulation staircase three-phase output voltages, and a three-phase induction motor as the load. In order to validate the proposed concept, simulation studies and experimental measurements using a small-scale laboratory prototype are also presented. The results show the feasibility of the fundamental frequency switching application in three-phase stand-alone PV power systems.

Performance of different types of renewable power supply systems

SYNOPSIS A combination of different types of generator has proved useful on technical and economic levels. In this paper we investigate the performance of a hybrid Photovoltaic(PV)-Wind generator power supply system operating under good and fair insolation and wind regimes. The effectiveness of such a hybrid system is measured by the Relative Sizing Parameter (RSP), Money Saving Parameter (MSP), and the Overall Reliability Parameter (ORP). Under specified weather conditions and for a nominal load demand, the RSP relates the product of the PV-modules and storage batteries involved in sizing the PV-Wind hybrid system to those of a stand alone PV-system sized to meet the same load. The MSP reports the difference between the total costs of a stand-alone PV power supply system and a hybrid PV-Wind power supply system, both sized to meet the same load, as a percentage of the total costs involved in supplying the load with a stand-alone PV power supply system only. The ORP compares the yearly average of the daily excess energy (positive difference between generated and consumed energy) of the hybrid system to that of the stand-alone PV power system. Based on this strategy we were able to develop a number of design diagrams which can be used in judging the benefits of utilizing hybrid PV-Wind generators on both economic and energy reliability grounds.