Impact Evaluation of Grid-Connected PV Systems on PQ Parameters by Comparative Analysis based on Inferential Statistics

Utility-interconnected Photovoltaic (PV) systems are quickly becoming a mainstay in today's energy portfolio and will conceivably achieve a level of penetration where operation and performance of these devices is likely to influence the operation of area electric power systems (EPS). To achieve this, PV systems need to harvest all available energy from the solar resource, channel this energy and convert it to usable power, and provide a high level of performance and interoperability all while maintaining a level of confidence and reliability that fulfill the vested interest in PV technology. High penetration of PV systems is realized through two distinctly different approaches; a high number of small residential PV systems at a given locality, or the more influential approach of a centralized PV power station, where a multi-megawatt PV installation is comprised by numerous commercial-sized inverters. This report is focused on the interaction of multiple residential utility-interconnected PV systems connected to a single distribution transformer. Four residential inverters have been connected to a point of common coupling (PCC) along with a single RLC load that will absorb the real power and provide a resonant tank circuit tuned to 60 Hz to be used for evaluating loss of utility. Determination of the interoperability in a high penetration configuration will be evaluated in a laboratory setting at Sandia National Laboratories' Distributed Energy Technologies Laboratory. The evaluations will focus on power quality, start up/shutdown routines, utility compatibility, and loss of utility functions. The direct current (dc) source will be provided by a Programmable Photovoltaic simulator that is designed to provide dc power with settable irradiance and module temperature conditions. An alternating current (ac) utility simulator will provide the necessary anomalies on the ac line to investigate the responses of the inverters under test.

This work presents an improved perturb and observe (P&O) algorithm based MPPT (Maximum Power Point Tracking) for a single stage solar photovoltaic (PV) array integrated with a three phase grid. Due to simple implementation and efficient tracking, the P&O approach of extracting maximum power from a PV array is very popular and efficient tracking technique among all MPPT techniques. However, the major pitfalls of this technique are that P&O MPPT is affected from drift, the outcome of drift occurring is much disapproving when there is a quick rate of increment in insolation. Drift takes place because of erroneous judgments taken by traditional P&O technique at the initial step alteration in voltage reference throughout the rise in insolation. An improved P&O algorithm is proposed here to improve the drift issue by deploying the details of variation in PV current (ΔDLI <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pv</inf> ) to make the judgment in extension to the variation in PV power (ΔDLP <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pv</inf> ) and variation in PV voltage (ΔDLV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pv</inf> ). In this PV system, a VSI (Voltage Source Inverter) and three phase grid are used. In a three phase distribution feeder network for indemnify, the quality of power as per an IEEE-519 standard on harmonics, it satisfies the power quality norms. So, for availing the real power feeding to the grid and to sustain the terminal voltage constant at the PCC (Point of Common Coupling) with sinusoidal grid voltages and grid currents, this system works well simultaneously with improved performance of P&O technique. The Matlab/Simulink is used for simulation and modelling of proposed system and the behavior of proposed MPPT algorithm has been examined for various insolation levels and different environmental situations on an experimental system which is established in the laboratory

The electrical system must adapt to the addition of distributed generation nodes in the networks. These generation nodes could influence the electric power quality and may affect the operation of the distribution networks. Grid connected photovoltaic (PV) systems are a good example of the increase of distributed generation. The impact of a PV plant in power quality parameters of a rural distribution network is shown in this paper. The characteristics of the PV plant and distribution network are listed and also the equipment used to carry out the measurements. Power quality parameters measured at the beginning of the grid are analyzed before and after to the PV plant connection. The voltages and currents waveforms are compared in both situations. Power quality parameters measured at the point of common coupling (PCC) of the grid and PV plant are shown and also the currents waveforms of PV inverters. The measures carried out on the grid show the influence of PV plant in the power quality of the distribution network. PV plants have introduced operational particularities in the networks that have to be considered for future PV grid connected regulation.

In future low voltage grids, with multiple inverter interfaced sources connected, voltage regulation may become a necessary task. The potential exists for inverter interfaced sources to be deployed to regulate the voltage at the point of common coupling (PCC) of each inverter interfaced sources. The PCC voltage regulation is attainable with inverter interfaced sources by dynamically controlling the amount of reactive power injected to the power distribution grid by individual systems. In the current research, a closed-loop controller is proposed to regulate the PCC voltage of a solar photovoltaic (PV) system that is connected to a single-phase power distribution feeder (with R to X ratio greater than 1). The plant model of the PCC voltage controller of the PV system is derived considering both reactance and resistance of the network to which the PV system is connected. Three different compensators are evaluated to identify a suitable compensator for the closed-loop PCC voltage controller to regulate the PCC voltage at a given reference voltage. Simulation studies and experimental verification confirm that the theoretical approach taken to derive the control plant model of the PCC voltage controller is accurate and the procedure that is followed to design the controller is robust. The control design procedures illustrated in the current research leads to a PCC voltage control system with acceptable dynamic and steady state performance.

Over the last decade governments in Australia and around the globe have heavily promoted the installation of rooftop solar photovoltaics (PV) in residential low voltage (LV) distribution networks. While distributed solar PV offers a range of benefits, they have not significantly reduced distribution network demand during critical periods due to the incongruity between the residential load profile and the solar PV generation curve. The residential load profile has load demand in the morning, moderate demand during mid-morning, low demand during the middle of the day and peak demand in the evenings. In winter the mid-morning demand is greater than in summer leading to instances where there are two peak demand periods during the day. Solar PV generation is low during the morning and steadily increases until the middle of the day and then decreases until the evening. Peak solar PV generation typically occurs when demand in the network is low. This entails that solar PV resources are poorly utilised and high concentrations of solar PV generation in LV distribution networks can often lead to the degradation of power quality through overvoltage and instances of reverse power flow. Moreover, the addition of solar PV to existing LV networks with unbalanced phases can often exacerbate existing power quality issues in a particular overloaded phase. Corrective measures to address power quality issues may require costly augmentations to the electricity network.

In this work, a Novel Adaptive Filter (NAF) is proposed for optimal control of grid-integrated solar PV (Photovoltaic) generating system. The proposed NAF is the improved form of classical adaptive vectorial filter (AVF), where inherent problems of AVF technique, like unable to handle the phase imbalance and phase shift issues, are successfully mitigated. For performance evaluation of NAF based control technique, a single-stage topology of three-phase grid integrated solar PV system is taken, where the loads are connected at the PCC (Point of Common Coupling). The prime objective of proposed NAF based control technique is to meet the active power requirement of loads from generated solar PV power, and after fulfill the load demand, the excess power is supplied to the grid. However, when generated PV power is not sufficient for the load then the NAF based control fulfills the load demand by taking extra required power from the grid. During this process, the power quality of the grid power is improved. The controller action provides, power factor correction, harmonics filtering and mitigation of other power quality issues. Moreover, when the solar irradiation is zero, then the voltage source converter acts as a distribution static compensator (DSTATCOM), which enhances the utilization factor of the system. The proposed techniques are modeled and their performances are verified experimentally on a developed prototype, in solar insolation variation conditions, unbalanced loading, as well as in different grid disturbances such as overvoltage, under-voltage, phase imbalance, harmonics distortion in the grid voltage etc.

In the Research Center (CINVESTAV), located north Mexico City was evaluated 60 kWp photovoltaic (PV) system. The PV system energy performance ratio, so called “quality factor” are reported together with the measured solar irradiation, ambient and PV module temperatures. Quality factor defines the overall system performance with respect to the energy production, solar resource, and total effect of system losses. The electric grid-tied PV system consists of 240 PV modules of 250 Wp each, which are connected to 5 inverters to produce three phase AC. We describe the general PV system quality factor in a month basis for 2013. In spite of the different seasonal weather conditions and some inverter trouble, the calculated average quality factor was 91.75%. The averaged daily PV generated energy throughout the year was 258.9 kWh/day. The accumulated total generated energy during the year was 94,427.7 kWh. However, instead of using solar irradiance sensor at the array tilt angle, and taking in consideration the horizontal global irradiation, the quality factor reduces drastically to 83.56%.

The renewable energy sources are intermittent in nature with high availability-based uncertainties. These resources when integrated to the utility grid significantly hinder the grid power quality (PQ). This article deals with PQ issues arising in the topology including the grid connected renewable energy generating system, which is a combination of wind turbine (WT) driving the synchronous generator (SG) and solar photovoltaic (PV) array and control strategies to improve the same. The solar PV array is associated at the dc link eliminating the dc–dc converter stage via a common dc link. The variable revolutions per minute (RPM) operation is achieved by the back to back connected grid side VSC (GVSC) and the machine side voltage source converter (MVSC). The GVSC is controlled by using the nonlinear harmonic observer (NHO) control. It provides robust implementation at various perturbations faced practically, i.e., discontinuous jump of frequency, phase, and amplitude. The fundamental load current component is effectively extracted. The NHO control is deployed within the framework to allow the system to dynamically adapt to the changes in the operating environment while maintaining the PQ of the utility grid. A special attention is paid to the condition when the power generated by the solar PV array is zero (during night operation) and the GVSC acts in the distribution static compensator (DSTATCOM) mode fulfilling the reactive power requirement. The regulation of MVSC is achieved by the vector control. Independent optimal power extraction techniques are featured for both wind and solar PV array. Test conditions are realized on the laboratory developed prototype and test results are acquired for PQ, loss of supply from solar PV array, effects of randomness of the wind speed, and solar insolation along with load alterations.

Monitoring and diagnosis of power quality is an important aspect in studies pertaining to the performance of a photovoltaic (PV) system. This research analyzes the role of a mixed snubber circuit in reducing the conducted electromagnetic interference (EMI) emissions on a charge controller of a low power, standalone, PV system connected to a common DC bus. The mixed snubber circuit has been found to suppress the conducted EMI and reduce power dissipation in a MOSFET when connected across a MOSFET-based buck converter. This research reports the effects of the conducted EMI for varying ranges of duty cycle of the buck converter for achieving maximum power tracking. This research has been carried out on a standalone, 4050 W PV plant, and the conducted EMI has been measured in real time and also verified by carrying out a simulation using PSPICE software to ascertain the effectiveness of the mixed snubber circuit. The results of the simulation were found to be in agreement with the results of various experimental studies. The exhaustive analysis indicates that the mitigation of EMI is due to the addition of the mixed snubber circuit along with the MOSFET-based converter arrangement.

This paper presents modeling of existing proprietary-based 1.6 kWp single-phase grid-connected photovoltaic (PV) system in Electrical Energy Conversion Research Laboratory (EECRL) of School of Electrical Engineering and Informatics (SEEI), Institute of Technology Bandung (ITB). The PV system was a grant from Indonesia State Utility Company (PT. PLN), included with the propietary inverter. Although it has supplied the energy to the laboratory, but detail study has not been conducted due to proprietary feature of the inverter unit. In this paper, an attempt to construct model to accurately represent the 1.6 kWp PV system of EECRL is presented. This modeling is useful to examine the performance of the 1.6 kWp PV system. Proposed modeling consist of PV array, DC-DC boost converter with maximum power point tracking (MPPT) feature, full-bridge DC-DC converter with galvanic isolation, and utility interactive DC-AC inverter. Simulation is conducted to verify part by part of the proposed model, comparison with actual result of the 1.6 kWp PV system is also conducted to verify the proposed model.

A PV (photovoltaic) controller is a device used in solar energy systems to manage the charging of batteries from solar panels efficiently. Total Harmonic Distortion (THD) reduction in PV (photovoltaic) systems is crucial for ensuring the efficient and reliable operation of the system while minimizing potential interference with the grid or other connected electrical equipment. This paper proposes an effective THD reduction model for PV applications. The proposed model incorporates the Unified Power Quality Conditioners (UPQC) for photovoltaic (PV). The UPQC in the PV is Optimized with the Seagull model for the estimation of values in the PV system. The optimization is performed with the Second-order derivatives of the Enhanced Second-Order Generalized Integrator (ESOGI). The derived model of the ESOGI model uses the Adaptive Neuro-Fuzzy Inference System (ANFIS) with SeaGull Optimization (SGO) for the voltage regulation in the PV system. The performance of the proposed model is implemented and tested with the different parameters illustrated that the performance of UPQC systems in terms of Total Harmonic Distortion (THD), Voltage Regulation, Power Factor Improvement, Reactive and Real Power Compensation, Voltage Stability, and Grid Stability. The proposed methodology demonstrates significant reductions in THD, tighter voltage regulation, enhanced power factor, and improved grid stability compared to conventional control techniques. The ESOGI-ANFIS-SGO optimization approach exhibits robustness and adaptability in handling variations in PV power output and grid conditions.

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.

Solar ship, which integrates the solar photovoltaic (PV) system into its own ship power system, is becoming one kinds of most promising and fastest developing green ship. Since the electric energy transformed by PV system is provided to the power load through the ship's distribution system, the output power of synchronous generator will be reduced in proportion. Especially, if the matching relationship among solar PV system, energy storage system and the power load requirement is precisely analyzed and the operation characteristics and reliability of solar inverter have already meet the strict test standards for marine equipment, the design capacity of synchronous generators could also be reduced. The off-grid mode and grid mode are the main way of integrated application of solar power photovoltaic system of ship. And the solar PV system is a kind of inverter power supply, which is essentially based on the electronic inverted technology, so PV system can be regarded as a ‘fragile power source’ with ‘zero inertia’. Therefore, the influence of solar photovoltaic grid-connected system to the power flow and power quality of the ship power system cannot be ignored. And the effect of photovoltaic system on the power quality of transient and steady-state and flow calculation remains to be studied. This paper mainly research the changes of power load flow calculation(PLFC) on the system, using the toolbox PSAT of MATLAB Simulink. This paper research the PLFC on the system of different solar photovoltaic systems access points, and analysis the experimental results. The results show that, under the premise of the normal operation of the ship electric power system, the improvement of the capacity of solar photovoltaic system in ship , and different access modes of photovoltaic grid-connected system, have slight impact on the power flow of power system, indicating that the photovoltaic grid-connected system in ship is stable, an appropriate increase in the capacity of PV system is feasible. The results is of certain significance of secure application of grid connected photovoltaic system in this paper.

Electrical Smart Grids (SG) contain numerous energy and operational measures, including renewable energy resources, energy efficiency resources, smart meters, and appliances. Investigating their applicability in a geographical area is important to provide a firm background to practical considerations. In this paper, the SG model is investigated, considering the available solar generation, hence enhancing residential load demand in Najaf city, Iraq. The analysis begins with an assessment of the electrical load profile characteristics, followed by choosing the optimum orientation of solar panels for the cities, which has been presented using MATLAB software. The optimum tilt angle for each month is estimated for three Photovoltaic (PV) systems of three sizes (1.5kWp, 2kWp, and 2.5 kWp). Furthermore, the study of their generation and impact on load demand is analyzed. The economic and financial analysis has been presented with payback period and benefits. The duck curve generated by the proposed PV systems is discussed. It is found that the annual demand saving of the proposed solar systems is 22%, 31%, and 36%, respectively. The hourly demand saving is presented, and it has been observed that there is overgeneration using 2kWp and 2.5 kWp PV systems, resulting in reshaping the load curve and producing the duck curve. The future work can be summarized by suggesting management of the battery system for the overgeneration.

Grid-connected photovoltaic system in Malaysia: A review on voltage issues