PQ analysis of a rooftop solar PV: a grid connected PV system pilot project in Indonesia

World electricity demand is continuously increasing and fossil fuel supplies are not sustainable. Solar Photovoltaic (PV) energy is one of the emerging resources around the world, which produces emission free electricity. Nowadays, the advancements in rooftop solar PV technology, government subsidies, decreasing capital cost and feed-in-tariffs have promoted installation in residential and commercial applications. The exponential uptake in widespread integration of PV systems in existing low voltage (LV) distribution networks is raising additional new challenges in terms of power quality, stability and protection. In LV distribution networks, poor power quality (PQ) is the most serious concern. Characteristically, LV distribution networks are not designed for significant back-feed of power generation to the main grid. Also, these networks are unbalanced in nature due to asymmetry in system impedances and single-phase loads. This together with a large number of small-scale PV system integrations in LV networks can cause poor PQ challenges in terms of voltage quality and harmonics. PV systems can themselves generate harmonics, due to the usage of power electronic inverters. In addition, the augmentation of power electronics based appliances; the loads are becoming voltage sensitive and nonlinear in nature. The proliferation of widespread PV penetrations and a multitude of nonlinear load characteristics can have a stringent impact on the network harmonic levels. Therefore, the main objective of this research is to investigate and understand the impacts of high PV systems penetration on PQ of the distribution network and aim to alleviate them. In the first part of this thesis, the investigation of voltage quality challenges in the LV distribution network with high PV penetration are discussed. In this research, various voltage quality issues such as voltage rise, unbalance, fluctuations/flicker and sag/swell issues have been explored. Primarily, the analysis of results has been carried out through PSCAD simulations in various case studies. For this purpose, an IEEE-13 bus unbalanced distribution network is considered as a test system. Furthermore, to evaluate the severity of voltage quality issues in real-time grid connected PV systems, field measurement based investigations have been performed. Practical field tests have been conducted at two different sizes of 1.5 MW and 3.3MW PV systems located at the University of Queensland (UQ), St Lucia and Gatton campuses respectively. The impact of dynamic variations in solar irradiation has also been taken into account for the analysis. Further, a data clustering technique is also applied to estimate the probability of voltage flicker severity in the networks. Measurement results show that voltage quality concerns in the 1.5MW PV system are insignificant compared to the 3.3MW system. In the second part of this thesis, the characteristics of harmonic emissions from PV inverters and their aggregations during various operating conditions are assessed. The simulation results are validated with the field measurement data collected by various PQ analysers connected at the UQ PV site. Analysis revealed that individual voltage and current harmonic magnitudes are additive in nature due to increased PV system penetration. In addition, a comprehensive analysis has been performed in several different cases studies with high penetration of different PV inverter technologies to evaluate the severity of harmonic propagation and resonance issues on the distribution network. This analysis has also considered the harmonic distortions associated with various power electronic based nonlinear loads. Further, comparative studies have been performed with real-time harmonic measurements, which are obtained using online JAVA programs. The study has highlighted the PV system harmonic contributions on distribution transformer K-factor. Results confirm that the total harmonic distortions (THD) of voltage and current are exceeding the IEEE limits when the number of PV systems increases in the network. Moreover, the impacts of PV controller performance due to solar irradiation variations on the incidence of grid harmonic resonance have been presented. Furthermore, this research has suggested a novel solution to overcome the above PQ issues. The concept of adopting the PV inverter as a virtual DSTATCOM named as Solar-DSTATCOM has been proposed. Also, a new control strategy for the PV inverter has been developed to provide independent phase voltage regulation and load reactive power and harmonic compensation, which could eliminate issues in the unbalanced distribution network. Initially, the Solar-DSTATCOM controller has been verified in a PSCAD simulation environment. Further, different case studies have been performed on the IEEE-13 bus network for PQ issues compensation. In addition, the proposed Solar-DSTATCOM control system has been tested and verified in controller hardware-in-the-loop simulation environment, which combines the real-time digital simulator and dSPACE DS1103 hardware board. Detailed investigations are carried out for various different case studies, which include daytime, night-time operations, the impact of dynamic load profiles and finally harmonic analysis. The analysis has revealed that Solar-DSTATCOM exceptional performance in the hardware environment has enhanced the grid PQ by providing voltage regulation, reactive power compensation and power factor correction. The harmonic emissions are well within the limits.

Photovoltaic (PV) systems are gaining importance in the present electrical distribution systems due to government policies and initiatives, hence the power production cost is also decreasing day by day. This paper focuses on the impacts of rooftop solar PV systems on secondary distribution system, which is rated to 30kW grid tied solar power plant. While studying the impacts of rooftop solar PV system on secondary distribution system, it is necessary to study power quality issues arising due to the integration of rooftop solar PV system and also possible solution to mitigate power quality problems. The study has been done on three different cases, first with the 30kW grid tied solar PV system alone, then 30kw grid tied solar PV system with 5 rooftop PV added to the system, finally 30kw grid tied PV system with 5 rooftop PV system with and without adding hybrid filters to the system and the results are obtained using MATLAB which shows the reduction in harmonics after the addition of hybrid filters to the system. Also, an advanced net metering is modelled in this paper which enforces the consumers to install harmonic filters to bring down the THD within limits, thus the consumer will have to pay penalty charges if the THD value exceeds the permissible levels.

With rapid increase in installation of rooftop Solar Photovoltaic (PV) systems in low voltage (LV) distribution networks, power quality becomes a key area of interest. Among various poor power quality problems in LV networks, harmonic distortions, which could come from several sources, have become a major concern. The solar PV systems can generate harmonics itself. Besides this, the increasing use of power electronics based nonlinear loads and PV system penetrations in the network inducing harmonics lead to poor power quality resulting in overheating of equipment and malfunction of controls. In this paper, harmonic distortion issues accompanied with solar PV inverter due to variations in solar irradiance has been thoroughly analyzed. Simulations have been performed in IEEE-13 bus distribution system with nonlinear loads to examine the harmonic emissions from conventional PV system for varying solar condition. To verify the simulation results and capture the trends harmonic measurements were made at the University of Queensland 1.2 MW PV site. The paper has also proposed a control algorithm for the harmonic compensation. Simulation results confirm that the proposed controller has effectively eliminated the harmonic issues for varying solar conditions.

Transient PV System Models for Power Quality Studies

Solar generation is a prominent source of renewable energy and a rooftop Photovoltaic (PV) system has been deployed in shipyard to generate electricity from the highest irradiance, which is in Tuas, West Region of Singapore. This is based on industrial rooftop PV system with bigger capacity of Battery Energy Storage System (BESS) in grid-connected PV system, is able to achieve greater cost saving for electrifying to load. This whole system is then modelled with simulation to demonstrate using discharging characteristics of the BESS under six different connection scenarios. The transient stability of PV with greater capacity of BESS can improve quality of the power flow to load when there is a sudden loss of power from PV. In addition, result shows that power quality will vary if there is more capacity in BESS integrated with PV.

- Power quality (PQ) is a critical aspect of electrical systems, especially in renewable energy applications like photovoltaic (PV) systems connected to the grid. A grid-connected PV system can introduce various power quality disturbances such as voltage sags, harmonics, flicker, and frequency deviations. This study investigates the power quality performance of a grid-connected PV system under different operational conditions. The analysis includes monitoring and evaluation of voltage, current, power factor, harmonics, and other electrical parameters to assess their compliance with established international standards. The impact of irradiance variations, temperature changes, and system configuration on the overall power quality is also examined. Furthermore, the integration of power quality improvement techniques, such as the use of filters and advanced inverter control strategies, is explored to mitigate these disturbances and improve system performance. The findings highlight the importance of efficient power quality management in ensuring reliable operation and smooth integration of PV systems with the electrical grid. The study further emphasizes the importance of proper grid synchronization techniques and real-time monitoring systems that enable operators to detect and address power quality problems promptly. The integration of real-time sensors and smart grid technologies can provide early warnings about power quality degradation and enable corrective actions before any major damage occurs. Moreover, this research highlights the role of standards and regulations in ensuring the compliance of PV systems with acceptable power quality levels. The study draws on international standards such as IEEE 519 and IEC 61000 to evaluate the extent to which grid-connected PV systems adhere to these guidelines. Finally, this work aims to contribute to the ongoing efforts to improve the reliability and stability of power grids incorporating renewable energy sources. By identifying the specific challenges associated with PV system integration and proposing viable solutions, this research supports the development of more resilient and efficient power grids that are capable of accommodating a higher share of renewable energy without compromising power quality. Keywords: Power Quality, Grid-Connected PV System, Harmonics, Voltage Sag, Inverter Control, Renewable Energy, Power Factor, Flicker, System Configuration, Photovoltaic, Electrical Disturbances.

Harmonic components have developed in power systems due to the non-linear properties of the circuit components utilized in power electronics-based products and their rapid application. Power systems rely on fundamental quantities like sinusoidally varying voltage and current, which oscillate at a frequency of 50 Hz. The standard restrictions of IEEE-519-1992 were utilized as a benchmark in this study. To generate the best output, the total harmonic distortion (THD) should be decreased below the limit, even for certain individual harmonic numbers, and reflect the power factor output. Using the results of the simulation and projections for each mitigation strategy, the THDI can be reduced below the IEEE-519 standard whilst also providing cost and electrical advantages. Analysed and modelled is the PV system, which comprises solar panels, a DC-DC converter, a DC-AC inverter, and a non-linear load. Passive filters are an effective solution for improving power quality in standalone photovoltaic (PV) systems. This dissertation provides an overview of the design and application of passive filters for this purpose. Firstly, an introduction to PV systems and the power quality issues associated with them was preferred. Next, different types of passive filters, namely LC filters, LCL filters and LLCL filters, are discussed along with their advantages and disadvantages, and the design considerations for these filters, including the selection of filter components and the calculation of filter parameters. The application of passive filters in standalone PV systems was then discussed, including their implementation in DC-DC converters and Z-Source inverters and, the design of PWM controllers such as the constant boost control method and simple boost control method. The analysis of the outcome of the engineered systems was conducted according to the IEEE standard and SANS 10142 Standard to protect the connected equipment within the off-grid network. The outcomes pertain to the single-phase stand-alone/off-grid photovoltaic system and the single-phase Z-Source inverter. The Z-Source inverter is equipped with two distinct methods for PWM control, namely the constant boost control method and the simple boost control method. All three designs incorporate three passive filters, namely the LC filter, the LCL filter and the LLCL filter. The results were obtained from the network consisting of three distinct designs. LLCL demonstrates superior performance as a passive filter, substantiating its position as the optimal choice. The optimal outcomes of a single-phase off-photovoltaic (PV) network can be achieved using LC, LCL and LLCL filters, with corresponding percentages of 2.99%, 2.45% and 1.71% respectively. Unfiltered was 89.05%, which is not good for the equipment connected to the network. The Z-Source showcases the capability of voltage amplification to an infinite level, rendering it highly effective in minimizing total harmonic distortion. This research investigation further demonstrated the efficacy of the Z-Source Inverter with Constant Control Boost Method and Simple Boost Control Method, achieving unfiltered total harmonic distortion levels of 38.85% and 44.96% respectively. The Z-Source inverter, when combined with the Constant Boost Control method and Simple Boost Control method, exhibits various filter configurations such as LC, LCL, and LLCL filters. In the context of the constant boost control and simple boost control methods, it is imperative to assess the total harmonic distortion percentage of voltage and current for LC, LCL, and LLCL configurations. The constant boost control voltage (LC, LCL, LLCL) and current total harmonic distortion (LC, LCL, LLCL) are measured at 4.177%, 2.655%, 1.951%, and 2.958%, 2.09%,1.465% correspondingly. The voltage-based boost control methods, namely LC, LCL and LLCL, exhibit total harmonic distortion levels of 2.345%, 1.920% and 0.211%, respectively. Similarly, the current-based boost control methods, LC, LCL and LLCL, demonstrate total harmonic distortion levels of 2.346%, 1.921%, 0.211%, and 2.346%, 1.921%, 0.211%, respectively. Finally, the dissertation wrapped up by exploring the potential of passive filters for enhancing power quality in standalone PV systems. The thesis offers a comprehensive investigation of the design and implementation of passive filters in standalone PV systems, providing valuable insights for engineers and researchers in the field. It enhances understanding and utilization of these imperative devices.

Power quality recognition in distribution system with solar energy penetration using S-transform and Fuzzy C-means clustering

This paper presents and discusses the monitoring of power quality of the first grid connected PV system in Algeria, installed in the rooftop of Centre de Developpement des Energies Renouvelables in Bouzareah, Algiers. This work is a part of the study of increasing penetration levels of distributed grid-connected photovoltaic (PV) systems in Algerian electrical distribution grid. Theoretically, this will have an impact on the grid that must be considered. The increase of the PV systems in distribution grid induces the consideration of aspects related to safety, protection and power quality. The experimental measurements concerning the active power, reactive power, power factor and total harmonic distortion (current and voltage) were performed at Point of Common Coupling (PCC) of the considered PV system. Generally, this PV system has negligible impact on the local grid; nevertheless, it is a very useful platform to study the power quality in Algerian distribution grid. The measurements were presented and discussed for different days, in order to observe the power quality behavior at PCC of CDER PV system. We find that the injection of PV power decreases the total harmonic distortion (THD) current of the electrical line.

Development of photovoltaic (PV) system in distribution network has increased rapidly in recent years. However, the high penetration of PV system may lead to voltage quality problems. Reactive power capability of inverter in PV system may be used to overcome these problems. However, there are several disadvantages that can arise due to reactive power existence in inverter PV such as an increase in internal loss of inverter, active power curtailment, and lifetime reduction of inverter. To compensate these problems, several reactive power incentive models are proposed. However, there is still no review about the current research about reactive power dispatch using inverter of PV system in distribution network as well as reactive power incentive model. Therefore, this paper contributes in providing an insight about the existing research about reactive power dispatch using inverter of PV system in distribution network as well as reactive power incentive model. This paper can be used as a guide to conduct future research about reactive power management using inverter in PV system.

Solar photovoltaic (PV) system installations are rapidly increasing in distribution networks. These PV systems include power electronic devices which have an influence on the power quality of the grid in the form of harmonic distortion. The aim of this study is the harmonic impact of PV systems on distribution networks. A comprehensive harmonic behaviour analysis has been performed on the IEEE‐13 bus distribution network with high PV systems penetration. A certain level of harmonics is also injected into the IEEE network through non‐linear loads to resemble a realistic scenario. The investigation has been carried out through simulations of three case studies, namely PV system integrations at a single node in particular with and without the presence of background distortions in the supply and finally PV penetration at multiple nodes with supply distortions. Furthermore, an evaluation study has been conducted at the University of Queensland PV site to validate simulation results. This study has highlighted the PV systems harmonic contributions on real distribution networks and the impact of harmonics propagation on transformer K ‐factor. Results show that the total harmonic distortions of current and voltage are exceeding the limits when the number of PV systems increases, leading to transformer overloading and heating.

Abstract- A solar PV (Photovoltaic) array, a battery energy storage (BES), a diesel generator (DG) set, and grid-based energy storage are all discussed in this study.The EV charging station (CS) is used to offer the constant supply of electricity.Charging modes include islanded, grid connected, and DG set connected.The charging station is primarily intended for solar power.To charge the electric vehicle, a solar PV array and a BES are used.(Electric vehicle) battery However, if the storage battery is depleted and charging station, solar PV array generation not available smartly utilises grid or DG power (Diesel Generator) set. However, the DG set's power is extracted in such a way that to ensure maximum fuel efficiency, always operate at 80-85% loading efficiency in any loading situation. Furthermore, without using a mechanical speed regulator, the charging station manages the generator voltage and frequency in conjunction with the storage battery. Even during nonlinear loads, it assures that the power drawn from the grid or the DG set is at unity power factor (UPF). Furthermore, to provide continuous charging, the PCC (Point of Common Coupling) voltage is synchronised to the grid/generator voltage. For increased charging station operational efficiency, the charging station also performs vehicle to grid active/reactive power transfer, vehicle to house, and vehicle to vehicle power transfer. The charging station's operation is experimentally tested using a prototype created in the lab. EV Charging Station, Solar PV Generation, Power Quality, DG Set are all index terms.

Interest in utility-interactive photovoltaic (PV) inverter systems has increased over the past decade and numerous central-station PV systems have been installed. It is anticipated that as PV system costs decrease, residential systems will be installed in increased numbers. Although a substantial amount of literature is available concerning the design, protection, safety, economics, and operating experience of residential and central-station PV systems, little information is available regarding their dynamic electrical characteristics and the computer modeling of these systems. Moreover, most of the available literature concerning modeling and/or dynamic performance focuses either upon the long-term dynamic behavior as it affects power system scheduling or upon the steady-state harmonic characteristics. In recent work, highly detailed computer models of a representative set of PV systems have been developed and several of these models have been verified by comparison with system measurements [1, 2]. However, the models described in [1, 2] are more complex than necessary for large-scale power system studies in which the fast switching transients associated with the dc-to-ac inverter are of little concern and only the slower cycle-to-cycle behavior of the PV system is of interest. In fact, it is not possible to incorporate these detailed models into conventional transient stability programs due, in part, to the very small time-step requirements associated with these models. In this paper, a three-phase self-commutated utility-interactive photovoltaic inverter system is described including its associated control system. A schematic diagram of the selected PV inverter system is depicted in Fig. 1.

Distribution static compensator is based on power electronic devices technology which is utilized to supply rapid changes in active power as well as reactive power of utility grids. This is useful to achieve corrections in power factor, balancing of load, compensation of current and filtering of harmonics. Therefore, proposed work investigates the improvement of the power quality by utilizing the distribution static compensator, which is equipped by battery energy storage system and interfaced to distribution network with solar photo voltaic (PV) energy integration. In the present study, distribution static compensator is controlled using a control strategy based on the synchronous reference frame theory. Customised IEEE‐13 nodes test system incorporating solar PV generation and distribution static compensator, is utilized to perform the harmonic mitigation and power quality analysis. Disturbances of power quality and harmonics have been investigated due to abrupt changes in the insolation of solar radiation, outage of PV plant from grid and synchronization of PV plant to grid. MATLAB/Simulink environment is utilized to perform the study. Effectiveness of a developed approach is validated by comparing results of simulation with results extracted in real time using real time digital simulator. Results indicate that the developed method is more effective for harmonic mitigation and improving power quality of electrical power in distribution network integrated with solar PV generation. Performance of the approach is compared with the performance of methods reported in the literature to establish the suitability of the method for harmonics mitigation and power quality improvement in grid with solar energy.

<abstract> <p>One of the most important areas in today's world is meeting the energy needs of various resources provided by nature. The advantages of renewable energy sources for many application sectors have attracted a lot of attention. The majority of grid-based enterprises use solar photovoltaic (PV) systems to collect sunlight as a reliable energy source. Due to solar PV's simple accessibility and efficient panel design, it is widely used in a variety of application scenarios. By employing the Maximum Power Point Tracking (MPPT) technique, the PV modules can typically operate at their best rate and draw the most power possible from the solar system. Some hybrid control mechanisms are utilized in solar PV systems in traditional works, which has limitations on the problems of increased time consumption, decreased efficiency, and increased THD. Thus, a new Mine Blast Optimization Algorithm (MBOA) based MPPT controlling model is developed to maximize the electrical energy produced by the PV panels under a different climatic situations. Also, an interleaved Luo DC-DC converter is used to significantly improve the output voltage of a PV system with a lower switching frequency. A sophisticated converter and regulating models are being created to effectively meet the energy demand of grid systems. The voltage source inverter is used to lower the level of harmonics and ensure the grid systems' power quality. Various performance indicators are applied to assess the simulation and comparative results of the proposed MBOA-MPPT controlling technique integrated with an interleaved Luo converter.</p> </abstract>