Grid-tied Solar Photovoltaic System Research Articles

A Multiple Improved Notch Filter-Based Control for a Single-Stage PV System Tied to a Weak Grid

In this paper, a control scheme based on improvement in a generalized integrator is implemented on a three-phase single-stage grid-tied solar photovoltaic system with the distribution static compensator capabilities under grid abnormal conditions of voltage distortion and voltage unbalance. The photovoltaic voltage-source converter system compensating for the reactive power consumed by nonlinear load at point of common coupling provides load balancing and mitigates harmonics. The proposed multiple-improved-notch-filter-based quadrature signal generator control approach extracts the load current fundamental component, independent of the grid voltage. This control has better dc offset and harmonics component rejection capability in comparison to a conventional second-order generalized integrator algorithm. The perturb and observe-based maximum power point tracking algorithm is applied for the extraction of maximum power from the photovoltaic array. The system is analyzed under different abnormal conditions of voltage distortions, voltages unbalance, voltage swell, voltage sag, load currents unbalance, and insolation change on a prototype developed in the laboratory. The system performance is found to be satisfactory, within limits as described in an IEEE-519 standard while feeding active power to distribution network and connected loads.

Active Power Control of Grid Tied SPV System with DSTATCOM Capabilities

AbstractThis paper presents an active power control of SPV (Solar Photovoltaic) grid tied system with the DSTATCOM (Distribution Static Compensator) capabilities using recursive least square (RLS) control algorithm with IC (Incremental Conductance) maximum power point tracking. The system serves dual purpose of working as a SPV-DSTATCOM and DSTATCOM in presence and absence of solar power, respectively. The SPV-DSTACOM provides compensating currents along with active current component thus fulfilling active power demand of connected load and feeds active power to the grid along with improving the power quality. Moreover, when the solar power is not available during night or low solar irradiation conditions, the system works as a DSTATCOM providing compensating current which improves the power quality of the system during load unbalance, harmonics and reactive power. A RLS based adaptive algorithm is used to do these functions at good convergence than conventional LMS (Least Mean Square) algorithm. Thus, the proposed system is capable to meet peak power demand when the solar energy is available and it improves the system power quality during day and night. The system responses under varying conditions is demonstrated on s developed prototype.

Experimental Investigation of Harmonics in a Grid-Tied Solar Photovoltaic System

The power quality issues in the grid tied solar photovoltaic system are important to address to know the actual power production and consumption in the existing system. This paper investigates the presence of voltage and current harmonics due to the linear, nonlinear loads and the reactive power transferred between plant, grid and load. The digital power analyzers are kept in the system to know the amount of power import and export between the plant and grid, so as to serve the load. In order to control the effect of harmonics a compensator in incorporated in the phase locked loop of the inverter as well as a power quality conditioner is connected at the point of common coupling. It has been found that by switching the compensator unit, the quality of power and power factor of the system gets improved and it also reduces the export of reactive power to the load so as to obtain the reliable and efficient operation of the grid tied solar photovoltaic system.

Multivariate Statistics and Supervised Learning for Predictive Detection of Unintentional Islanding in Grid-Tied Solar PV Systems

Integration of solar photovoltaic (PV) generation with power distribution networks leads to many operational challenges and complexities. Unintentional islanding is one of them which is of rising concern given the steady increase in grid-connected PV power. This paper builds up on an exploratory study of unintentional islanding on a modeled radial feeder having large PV penetration. Dynamic simulations, also run in real time, resulted in exploration of unique potential causes of creation of accidental islands. The resulting voltage and current data underwent dimensionality reduction using principal component analysis (PCA) which formed the basis for the application ofQstatistic control charts for detecting the anomalous currents that could island the system. For reducing the false alarm rate of anomaly detection, Kullback-Leibler (K-L) divergence was applied on the principal component projections which concluded thatQstatistic based approach alone is not reliable for detection of the symptoms liable to cause unintentional islanding. The obtained data was labeled and aK-nearest neighbor (K-NN) binomial classifier was then trained for identification and classification of potential islanding precursors from other power system transients. The three-phase short-circuit fault case was successfully identified as statistically different from islanding symptoms.

A Three-Phase Grid Tied SPV System With Adaptive DC Link Voltage for CPI Voltage Variations

This paper deals with a three-phase two-stage grid tied SPV (solar photo-voltaic) system. The first stage is a boost converter, which serves the purpose of MPPT (maximum power point tracking) and feeding the extracted solar energy to the DC link of the PV inverter, whereas the second stage is a two-level VSC (voltage source converter) serving as PV inverter which feeds power from a boost converter into the grid. The proposed system uses an adaptive DC link voltage which is made adaptive by adjusting reference DC link voltage according to CPI (common point of interconnection) voltage. The adaptive DC link voltage control helps in the reduction of switching power losses. A feed forward term for solar contribution is used to improve the dynamic response. The system is tested considering realistic grid voltage variations for under voltage and over voltage. The performance improvement is verified experimentally. The proposed system is advantageous not only in cases of frequent and sustained under voltage (as in the cases of far radial ends of Indian grid) but also in case of normal voltages at CPI. The THD (total harmonics distortion) of grid current has been found well under the limit of an IEEE-519 standard.

Power quality analysis of a large grid-tied solar photovoltaic system

Over the last decades, the deployment of large solar-based photovoltaic power plants has grown tremendously. The undesirable impact of high integration level of photovoltaic systems has led energy stakeholders to regulate such penetration to avoid this negative impact. One major concern with regard to photovoltaic penetration is the issue of power quality. Poor power quality can be a source of system disturbance and major economic losses. However, the power quality analysis is not widely discussed in the literature, with most of the studies focusing on the harmonic issues as potential power quality problem, but this study shows that there are a number of power quality issues, such as undervoltage, overvoltage, power fluctuation, and power factor. This study presents practical approaches to a grid-connected solar photovoltaic plant with associated control circuits developed in the time-domain. The power quality of a grid-connected solar photovoltaic plant is investigated by an analysis of the inverter output voltage and nominal current for different photovoltaic plant sizes. Also, the effect of different conditions of solar irradiance and ambient temperature on the power quality is analyzed. To identify power quality issues, a photovoltaic plant time-domain model is developed using Power Systems Computer Aided Design software. Various solar photovoltaic plant controls such as maximum power point tracking and modulation signals sinusoidal pulse width modulation and pulse width modulation for direct current-to-direct current boost converter are developed and integrated into the simulation environment. Several case studies are performed taking into account different photovoltaic plant ratings such as 250 kW–3 MW, where the point of common coupling is monitored.

Combined Effect of Deterministic and Stochastic Variables on Comparative Performance Analysis of 110 kW A-Si PV and C-Si PV based Rooftop Grid Tied Solar Photovoltaic Systems in Jodhpur

The main objective of this paper is to review the state of the art of IIT Jodhpur Rooftop installed 110 kW PV systems. This is done analyzing the operational data of 110 kW PV systems (43.30 kW located in Block 1 and 58.08 kW in Block 2). Performance analysis depends on three basic term of solar PV. How much energy do they produce? What level of performance is associated to their production? Which are the key parameters that most influence their quality? During the year 2011, the PV systems in Jodhpur, India have produced a mean annual energy of 1290.64 kWh/kWp in block-1 and 1290.64 kWh/kWp in Block-2. As a whole, the location of Solar PV system is the main reason of energy variability and system output. The overall mean Performance Ratio is 75% in both Blocks. Solar power variability depends on the two variables, deterministic and stochastic variable. In last few years researcher work on finding deterministic variable such as system losses (module efficiency, DC cable losses, inverter losses and AC cable losses) but these deterministic variables are not enough to give accurate forecasting so with the help of combined effect of these both variable give accurate plant performance and reliable solar power forecasting for solar power scheduling and dispatchability.