Connected Photovoltaic System Research Articles

Dandelion Optimizer-Based Reinforcement Learning Techniques for MPPT of Grid- Connected Photovoltaic Systems

Dandelion Optimizer-Based Reinforcement Learning Techniques for MPPT of Grid- Connected Photovoltaic Systems

Analysis of power quality and economic worthiness of electric motorcycle charging in a residential electrical system

AbstractIn the urban society of Thailand, most people use motorcycles for travelling because they can meet the manoeuvrability of travelling in short distances and save energy compared to using a car. Many people are switching to electric motorcycles (EMCs), which install EMC chargers in their residential buildings. EMC chargers are power electronic devices that may produce electrical and electromagnetic interference; therefore, it is critical to evaluate the potential influence of an EMC charger on a household electrical system and other electrical equipment before installing one. Therefore, this study examined the effects of an EMC charger on residential electrical systems with and without a photovoltaic system connection as well as on individual load types in terms of power quality. The investigation revealed that EMC charging has a direct impact on the grid system's reactive power, power factor, and current harmonics. However, when the electrical load in the system has sufficient power, it is possible to reduce the reactive power and current harmonics of the grid. The cost of electricity when an EMC is connected to a residential electrical system was also analysed to determine the metre type and charging interval suitable for Thailand.

Planning and Operation of an Intelligent Power Electronics Series Voltage Regulator for PV-Rich Distribution Feeders

The connection of photovoltaic systems on weak electrical distribution networks can lead to the occurrence of excessive overvoltages or undervoltages that lead toward unsatisfactory operating conditions for renewable energy producers. In such critical situations, where electrical parameters are outside standard regulatory levels, the untimely tripping of electrical protections can lead to losses of renewable energy production and thus to the reduction of producers’ economic revenues. In this context, this article describes aspects related to the planning and operation of an intelligent voltage regulator capable of solving voltage regulation problems in PV-rich low-voltage networks. The results achieved with the application of the power electronics device in electric distribution networks are shown with a real case study in a network with a high penetration of photovoltaic-type renewable energy installations. The results show the effectiveness of the application of the device considering both technical and economic aspects; these results are also compared with traditional distribution network planning strategies, highlighting the advantages for the distributor and the owners of photovoltaic systems.

Analysis of the Power Quality of a Grid-Connected Photovoltaic System

The use of Grid-Connected Photovoltaic Systems is increasingly on the rise in Brazil. Faced with this growth, it is necessary to evaluate the impacts of this source in the electric energy systems. Based on this scenario, the present work aims to analyze and quantify the impact of a grid-connected photovoltaic system connection, evaluating the Electric Power Quality indicators based on the levels specified in Module 8 of the Electric Energy Distribution Procedures in the National Electric System. To perform the data collection, an energy analyzer device was installed at the output of the grid-connected system inverter located in the Energy Laboratory of the Federal Rural Semi-Arid University, located in the city of Mossoró-RN. Using the collected data, it was possible to analyze parameters of voltage and current distortion, power factor, active, reactive and apparent power, voltage, frequency variations, and voltage unbalance. It was observed that the criteria analyzed were within the appropriate standards although there were also verified cases that there was an elevation in tension levels. Finally, it is concluded that the impacts caused are relevant within the electric system, and grid connected system performance was satisfactory, although there are still possibilities for improvements.

Coordinated active and reactive power control for overvoltage mitigation in physical LV microgrids

The share of photovoltaic (PV) systems in the distribution networks is rapidly growing, leading to the common issue of overvoltage at the end of distribution feeders during the periods when peak generation is surplus to consumption. In this study, a hierarchical control is proposed to mitigate overvoltage at the point of connection of PV systems in physical low-voltage microgrids. The proposed mechanism is comprised of primary and secondary control layers to tackle the overvoltage problems given the communication capability is available. This mechanism employs a multi-objective optimisation approach to effectively coordinate curtailed active power and absorbed reactive power of the PV inverters with the aim of minimising the active power curtailment. The feasibility of the proposed control approach is successfully verified through simulations on a simplified LV network.

Influence of local market economic analysis on PV generation stochastic approach in LV distribution networks

This work investigates the influence of the local photovoltaic (PV) market in the analysis of the photovoltaic distributed generation (PVDG) impacts on LV networks. The new methodology proposed by this work indicates: the PV penetration based on different scenarios and technology diffusion evaluation; the probability of technical violation occurrence due to PVDG connection; and the location of the critical points over the distribution system, aiding in the efficient management of investment in network reinforcements. The novelty of this methodology refers to the inclusion of an economic analysis within the stochastic approach, considering the influence of local market in the technical assessment. Furthermore, this methodology is applied to a real distribution feeder in Brazil. Firstly, an economic analysis of the consumers of the studied circuit is carried out to estimate the PVDG penetration. Next, Monte Carlo Simulations are performed through OpenDSS considering network parameters, real local irradiance and load curves measured by advanced metering infrastructure. Therefore, it is possible to consider the uncertainties associated with the connection of PV systems and the variation of consumer load. One of the main results of this study is that the proposed methodology notices less technical violations than the methodology that is traditionally used in the literature and does not consider the influence of the local market. In addition, technical violations tend to occur in different transformers for each methodology. This happens because the traditional methodology considers that every consumer has the same probability of installing PVDG, including those classified as not economically able according to the analysis proposed in this article.

Contribution of solar energy for the correction of the voltage drop recorded on a LV power grid in Algeria

ABSTRACT Generating electricity from solar energy can offer significant benefits especially for the rural population where the distribution of electric power suffers from voltage drop problems caused by isolation and difficult topography, so it is necessary to explore this new option, by exploitation of the abundant solar potential which has these areas. In this work we look for the optimal solution among two propositions: the first was to connect photovoltaic (PV) plants to medium voltage (MV) network, while the second is to connect mini-power plants in to low voltage (LV) network; this problem concerns a real case of voltage drop that affects a large rural area in the province of Chlef (North of Algeria). The obtained results show that the second solution can be used like an optimal solution. The connection of PV systems has improved the electrical quality of the line grace the injection into the network of clean solar power especially when the peak demand is in phase with the intensity of sunlight. Thus allowing contributes to the reduction of purchasing electricity needs.

Perspectives of modern energy storage in miniscule photovoltaic installations

In the research work environmental pollution information and idea of solution of this problem through renewable energy sources were presented. The methods of solar energy coversion as well as methods of its storage in lithium batteries were described. The work presents an analysis of energy system: solar panel and energy bank in households. The ecological aspect of this solution was studied. For this purpose, the costs of new single-family house connection to the energy grid and photovoltaic system connection with a modern lithium battery were calculated. Electricity consumption cost estimation within ten years was made and then it was compared to the expenses for connected photovoltaic system with lithium battery. Aim of the study was realized based on the cost of connection to the energy grid and the costs of photovoltaic system connection with Tesla batteries. From the above data one can see that after about 7 years with lower solar exposure level costs of the installation based on renewable energy sources installation will pay off and after that one can only record a profit from storing and producing electricity.

Photovoltaic DC yield maps for all Morocco validated with ground measurements

In Morocco, Law 58/2015 has legalized the connection of photovoltaic systems on the low-voltage grid and the country should probably be adopting the net-metering approach. Since the electricity distributor should only buy a7. small part of the electricity injected, system over-sizing becomes critical for the investor. In these conditions, it is critical to know the photovoltaic yield generated at any specific Moroccan location. The objective of this study consists on calculating, generating and drawing precise maps of grid-connected photovoltaic DC yields for three silicon technologies (monocrystalline, polycrystalline and amorphous) for all Morocco. For this, (i) we have measured and collected 2466 daily DC yields spread over 20 sites for each of the three technologies and validated three models matching the experimental measurements. Then, (ii) we have selected 1392 representative points covering all Morocco (resolution 0.25°) for which, the three validated models gave the long-term average of photovoltaic DC yields using appropriated input data from Solar Med Atlas. And finally, (iii) we have drawn the long term monthly average of daily PV DC yields maps with the help of ArcGIS set up to use the ordinary kriging method to interpolate between the 1392 points.

Modeling and design of photovoltaic power plant connected to the MV side of Malaysian grid with TNB technical regulation compatibility

Increasing penetration of photovoltaic power plants (PVPPs) to the electrical grid leads to continuous evaluation of grid interconnection requirements. For this purpose, Malaysian grid representative from Tenaga Nasional Berhad (TNB) issued technical rules and requirements concerning the connection of photovoltaic system to low and medium voltage networks. The objective of this paper is to design a large-scale PV plant connected to the MV side of the Malaysian grid, taking the compliance of TNB technical regulations into consideration. In this study, the PV plant has been modeled using MATLAB/Simulink with nominal rated peak power of 1.5 MW. The sizing of suggested PV system is achieved in which the simulation results matched the sizing calculation results. The paper focuses on the model’s ability to reflect the important requirements that a PVPP should have based on TNB rules for MV connection. The results show that the proposed PVPP is compatible with TNB requirements.

Connection of the CDER-Algiers photovoltaic system to low-voltage distribution grid

This work deals with the first photovoltaic (PV) system connected to the low voltage electrical grid in Algeria. The system is made of a PV generator and inverters, which convert the generated direct current into to alternating current, and injects it in the low voltage distribution network of Sonelgaz (Algerian electricity provider). The generated current is perfectly compatible with that supplied by the network. The power of the installed PV generator is 9.54 kWp. In order to produce this power, three sub-fields of I-106 modules are used. Each of these sub-fields is connected to an inverter. This work allowed the study of phenomena related to the PV system connection to the network, namely: power quality, reactive power, current THD and voltage, etc. Electrical parameters at the point of common coupling (PCC) were studied, including the impact of this PV installation on the grid.

Highlight of Grid-connected PV systems in administrative buildings in Egypt

Solar energy applications are becoming increasingly common in Egypt. The abundant sunshine in Egypt, as well as the increasing competitiveness of solar energy systems including- but not limited to photovoltaic (PV), – predicts that these technologies could be weighed to be raised in Egypt. PV systems are installed on roof tiles or other parts of building structures to supplement grid utility, reduce electric bills, and provide emergency back–up energy. Moreover, they simultaneously reduce significant amounts of CO 2 emissions. It is foreseen, a number of residential and public buildings in Egypt are using solar power to cut electric utility bills significantly. The approximately payback period to recover the investment costs for PV systems is up to about 5 years. In addition, it is more economical to use PV system than grid utility systems. The two components that determine the total initial price of a grid- connected PV system are the modules and the balance of systems (BOS). The BOS includes different components such as mounting frames, inverters and site- specific installation hardware. The Government of Egypt (GOE) has endorsed the deployment of PV systems through three approaches. It started with a prime minister decree to install PV projects on one-thousand of the governmental buildings. This was followed by as an initiative called "Shamsk ya Masr", and finally the Feed-in Tariff (FiT) projects. Following the prime minster decree the Egyptian Electricity Holding Company (EEHC) and its affiliated companies took the lead to install PV systems at the top roof of their administrative buildings and interconnect these systems to the electricity network where the suitable locations have been selected for mounting them. About 90 PV systems have been already mounted with about a capacity of 9 MW. On the other hand, "Shamsk ya Masr" has considered energy efficiency (EE) so as to complement the PV systems, which will be installed on administrative buildings. Cost- effective EE measures should be implemented prior to or at the same time as implemented PV program. The amount of electricity that a PV system produces depends on the system type, orientation and the available solar resource. In 2014, the GOE issued the Feed-in Tariff program to further promote RE technologies in general and PV in particular. Egyptian Electric Utility and Consumer Protection Regulatory Authority (Egypt ERA) has set the regulations, promotion and awareness for PVs. This approach has been applied for administrative buildings as well. The paper highlights the impact of the previously mentioned mechanisms in deploying PV technologies through small scale projects. It also represents a cost- benefit analysis for the installed systems taking into account the measured value for PV parameters (kWh/kWp, PSH) and daily load profiles of the selected administrative buildings.

Defining control strategies for photovoltaic reconnection in islanded microgrids

The increasing integration of photovoltaic systems in recent years challenges power systems with respect to their reliability, security and stability. Frequency stability is one specific problem. Sudden disconnects or connects of large amounts of photovoltaic systems without explicit countermeasures may result in substantial decrease or increase of the power system’s frequency. This can cause load shedding actions, disconnection of other generating units, or, as worst case, a black-out. These problems which occur after the disconnection and connection of photovoltaic systems are even more severe within islanded microgrids, because frequency changes quickly when there is a power mismatch due to their low system inertia. In this paper, an islanded microgrid, including a conventional generator, a photovoltaic array and a lumped load, is used as a study case to investigate the reconnection challenges of photovoltaic systems in those electrical networks with relative low inertia. Four different control scenarios, which regulate the strategy for photovoltaic reconnection, and their communication requirements are described, analyzed and compared.

English

This paper grants a effective analysis between the PI and fuzzy controllers when functioned through a single-phase five-level photovoltaic (PV) inverter configuration for grid- connected PV systems with newly developed modulated (PWM) control scheme. It employs two reference signals and a carrier signal to produce PWM switching signals. The inverter compromises much less total harmonic distortion and quick steady state response when coupled through a fuzzy controller. This paperobtainablefor a single-phase multilevel inverter for PV application. The circuit configuration, modulation law, and operational principle of the suggested inverter were examined in detail.MATLAB/SIMULINK results indicate that the THD of the Fuzzy Controller Circuit is much smaller than that of the THD of the PI Controller Circuit.

Fault Analysis of Grid Connected Photovoltaic System

A new method of current control strategy for grid connected photovoltaic (PV) system is presented in this paper. The connection of photovoltaic system with the grid is a difficult task as the solar irradiation is a nonlinear quantity. The objective of this work is to develop a model of the photovoltaic system with maximum power point tracking (MPPT) system connected to 11 KV grid by implementing new control technique so that maximum active power transfer from PV to grid can be taken place without injection of harmonics. The considered system consists of a PV system, MPPT controller, boost converter, voltage source inverter (VSI), 3-Φ filter, a control system, a distribution network, load and grid. In the beginning, a model of a photovoltaic array was developed and then a MPPT controller and a direct current to direct current (DC-DC) converter are designed. To connect PV system to grid, a power electronics converter is needed which can convert DC voltage into three- phase AC voltage. Three-phase VSI using insulated gate bipolar transistors (IGBTs) is used. By means of a step-up transformer and filter, this three-phase VSI is connected to the distribution network. The proposed control of the three-phase grid-connected solar PV system is designed in the synchronously-rotating d-q reference frame. Here, Vdc is measured, then compared with Vdcref and accordingly the error is fed to proportional-integral (PI) controller from which Idref is generated. As PV system should inject only active power, so reactive power injected to grid is made zero by making Iqref zero. There after the final model is simulated by using MATLAB/SIMULINK and different output waveforms are analyzed for different conditions. Finally the fault analysis is carried out to observe the behavior of the system.

Simulation study of parameter estimation and measurement planning on photovoltaics degradation

Photovoltaics degradation is one of the key parameters in PV performance evaluation. Units under a degradation study can be either modules or systems. As a single set of degradation measurements based on one unit cannot represent the population nor be used to estimate true degradation of a particular PV technology, repeated measures through multiple units are essential. Linear mixed effects model is a suitable tool for analyzing longitudinal data. In this paper, I use LME model to explain the degradations in PV modules/systems which are installed at a shared location with modules of same technology. The degradation parameters including degradation rate can then be estimated using maximum likelihood estimation. Beside the degradation rate, other parameters of interest, e.g., the degradation distribution quantiles, are also derived to provide valuable information for PV manufacturers and system owners. Two types of measurements describe PV degradation, namely, a regression-based low-accuracy measurement through monitoring data (such as solar irradiance, module temperatures and various electrical parameters) and the flash test which can be considered as a high-accuracy measurement. Given the underlying true degradation of a set of units, the two methods differ mainly in measurement accuracy. The error differences between the low- and high-accuracy experiments are analyzed through simulation.

Emission from small scale PV-installations on the low voltage grid

The use of solar panels is becoming more popular in Sweden. Parts of Scandinavia have many sun hours and the cold temperatures are advantageous as they lead to higher efficiencies and longer lifetimes of the solar cells. In this paper conducted emission levels associated with the connection of photovoltaic systems will be discussed. Harmonics (up to 2 kHz) and supraharmonics (2 to 150 kHz) will be discussed. Measurements from three phase connected plants (20 kW) and from smaller (up to 2.5 kW) single phase connected plants are shown. The harmonic emission from PV-plants is reasonably low and somewhat constant with regards to the production. Some residue from the switching of the inverter can be found typical at a few kHz.

Power Loss Comparison of Single- and Two-Stage GridConnected Photovoltaic Systems

This paper presents power loss comparison of single and two-stage grid-connected photovoltaic (PV) systems based on the loss factors of double line-frequency voltage ripple (DLFVR), fast irradiance variation + DLFVR, fast dc load variation + DLFVR, limited operating voltage range + DLFVR, and over- all loss factor combination. These loss factors will result in power deviation from the maximum power points. In this paper, both single-stage and two-stage grid-connected PV systems are considered. All of the effects on a two-stage system are insignificant due to an additional maximum power point tracker, but the tracker will reduce the system efficiency typically about 2.5%. The power loss caused by these loss factors in a single-stage grid- connected PV system is also around 2.5%; that is, a single-stage system has the merits of saving components and reducing cost, and does not penalize overall system efficiency under certain operating voltage ranges. Simulation results with the MATLAB software package and confirmed the analysis. Index Terms: Loss factor, power loss comparison, single-stage grid-connected photovoltaic (PV) system, two- stage grid-connected PV system.

Control Scheme for Photovoltaic Three-Phase Inverters to Minimize Peak Currents During Unbalanced Grid-Voltage Sags

Nowadays, the majority of the photovoltaic (PV) power sources are connected to the public grid. One of the main connection problems occurs when voltage sags appear in the grid due to short circuits, lightning, etc. International standards regulate the grid connection of PV systems, forcing the source to remain connected during short-time grid-voltage faults. As a consequence, during the voltage sag, the source should operate with increasing converter currents to maintain the injection of the generated power. This abnormal operation may result in nondesired system disconnections due to overcurrents. This paper proposes a controller for a PV three-phase inverter that ensures minimum peak values in the grid-injected currents, as compared with conventional controllers. From the system analysis, a design method is presented in order to set the parameters of the control scheme. Selected experimental results are reported in order to validate the effectiveness of the proposed control.

신뢰도를 고려한 태양광시스템의 배전계통 연계 알고리즘에 관한 연구

In this paper, when photovoltaic (PV) systems are connected to power distribution system, most effective capacity and connected-point of PV system are presented considering power distribution system reliability. The reliability model of PV system is presented considering the duration of sunshine. Also the model of time-varying load and reliability test system bus2 model are used. To simulate the effects of PV system, various cases are selected; (1) base case which is no connection of PV system to power distribution system when faults are occurred, (2) 3MW case which is 3[MW] connection of PV system (3) 4[MW] case, and (4) 20[MW] case which is 20[MW] connection of PV system to the bus of power distribution system. The capacity limit of connected PV system is settled to 14[MW] for all cases except case 4. The reliability for residential, general, industrial, and educational customer is evaluated