Major technical issues with increased PV penetration on the existing electrical grid

In the past decade, the installation of rooftop PV (Photovoltaic) systems has substantially increased in many countries. This increase is anticipated due to government incentives like RECs (Renewable Energy Certificates) and feed-in tariff, to counterbalance the carbon emissions and satisfy local energy needs provided to the customers. The existing electrical grid infrastructure was originally designed to supply power from source to load but now due to such increase of distributed PV generation there is the possibility of reverse power flow which presents some technical challenges when the numbers of such systems increase for the utilities. Out of all the technical issues, to analyse the effects of voltage rise on LV (Low Voltage) distribution side of the grid due to such systems is the main objective of this project. This paper considers data that is collected from 7 different grid connected solar PV systems that are installed in different suburbs of Perth, Western Australia and one outside Perth in Bridgetown, Western Australia in order to show that voltage rise on the feeder is a common effect wherever these systems are installed. The Australian Standards for grid connected PV systems are studied and what effects are caused when a number of such systems are increased on the grid. A number of options are suggested in order to lessen or overcome this effect some of which suggest revising the existing old standards for connection. The conclusion derived will be what are the necessary steps need to be taken in order to integrate future penetration of such distributed generation

Coordinated active power reduction strategy for voltage rise mitigation in LV distribution network

Integration of renewable energy systems by the utility, customers, and the third party into the electric power system, most especially in the MV and LV distribution networks grew over the last decade due to the liberalization of the electricity market, rising energy demand, and increasing environmental concern. The distributed rooftop PV system contributes to relieve the overall load, reduce losses, avoid conventional generation upgrade, and better matching of demand on the LV distribution network. Originally, the LV distribution network is designed for unidirectional current flow, that is from the substation to customers. However, a high penetration of rooftop solar PVs (with power levels typically ranging from 1 – 10 kW) may lead to the current flowing in the reverse direction and this could result in a sudden voltage rise. These negative impacts on the network have discouraged the distribution network operators (DNOs) to allow increased PV penetration in the LV distribution network because some customers load, and equipment are sensitive to voltage perturbation. Presently, the most applied voltage rise mitigation strategy for high rooftop solar PV penetration is the total disconnect from the LV distribution network when the voltage at the point of common coupling (PCC) goes above statutory voltage limits. However, the sudden disconnection of the PV system from the grid can cause network perturbation and affect the security of the network. This action may also cause voltage instability in the network and can reduce the lifetime of grid equipment such as voltage regulators, air conditioner etc. Due to this negative impact, different voltage rise mitigation strategies such as the active transformer with on load tap changers (OLTC), distributed battery energy storage system and reactive power support (D-STATCOM, etc.) have been used to curtail voltage rise in the distribution network. However, the implementation of D-STATCOM device on a radial LV distribution network results in high line current and losses. This may be detrimental to the distribution network. Therefore, in this thesis, a coordinated active power reduction (CAPR) strategy is proposed using a modified PWM PI current control strategy to ramp down the output power and voltage of a grid-tied voltage source inverter (VSI). In the proposed strategy, a reactive reference is generated based on the measured voltage level at the PCC using a threshold voltage algorithm to regulate the amplitude of the modulating signal to increase the off time of the high frequency signal which shut down the PV array momentary in an extremely short time and allow the VSI to absorb some reactive power through the freewheeling diode and reduce voltage. The proposed CAPR strategy was designed and simulated on a scaled down simple radial LV distribution network in MATLAB®/Simulink® software environment. The results show that the CAPR can ramp down the PV output power, reduce reverse power flow and reduce the sudden voltage rise at the point of common coupling (PCC) within ±5% of the standard voltage limit. The study also compares the performance of the proposed CAPR strategy to that of the distributed static compensator (D-STATCOM) and battery energy storage system (BESS) with respect to response time to curtail sudden voltage rise, losses and reverse power flow. The investigation shows that the D-STATCOM has the faster response time to curtail voltage rise. However, the voltage rise reduction is accompanied by high current, losses and reverse active power flow. The introduction of the BESS demonstrates better performance than the D- STATCOM device in terms of reverse power flow and losses. The CAPR strategy performs better than both D-STATCOM and BESS in terms of line losses and reverse power flow reduction

Impact of distributed generation on protection and voltage regulation of distribution systems : a review

During recent decades with the power system restructuring process, centralized energy sources are being replaced with decentralized ones. This phenomenon has resulted in a novel concept in electric power systems, particularly in distribution systems, known as Distributed Generation (DG). On one hand, utilizing DG is important for secure power generation and reducing power losses. On the other hand, widespread use of such technologies introduces new challenges to power systems such as their optimal location, protection devices' settings, voltage regulation, and Power Quality (PQ) issues. Another key point which needs to be considered relates to specific DG technologies based on Renewable Energy Sources (RESs), such as wind and solar, due to their uncertain power generation. In this regard, this paper provides a comprehensive review of different types of DG and investigates the newly emerging challenges arising in the presence of DG in electrical grids.fi=vertaisarvioitu|en=peerReviewed

Why Do Electricity Policy and Competitive Markets Fail to Use Advanced PV Systems to Improve Distribution Power Quality?

The increasing pressure for network operators to meet distribution network power quality standards with increasing peak loads, renewable energy targets, and advances in automated distributed power electronics and communications is forcing policy-makers to understand new means to distribute costs and benefits within electricity markets. Discussions surrounding how distributed generation (DG) exhibits active voltage regulation and power factor/reactive power control and other power quality capabilities are complicated by uncertainties of baseline local distribution network power quality and to whom and how costs and benefits of improved electricity infrastructure will be allocated. DG providing ancillary services that dynamically respond to the network characteristics could lead to major network improvements. With proper market structures renewable energy systems could greatly improve power quality on distribution systems with nearly no additional cost to the grid operators. Renewable DG does have variability challenges, though this issue can be overcome with energy storage, forecasting, and advanced inverter functionality. This paper presents real data from a large-scale grid-connected PV array with large-scale storage and explores effective mitigation measures for PV system variability. We discuss useful inverter technical knowledge for policy-makers to mitigate ongoing inflation of electricity network tariff components by new DG interconnection requirements or electricity markets which value power quality and control

Förderung des Aufbaus von Smart Grids in Thailand als Zusammenspiel von intelligenten Gebäuden, intelligenten Verbrauchern und einer intelligenten Energiepolitik

Smart grid technology can enhance renewable energy in the electricity system by integrating information communication technology (ICT) into the existing electricity network. Residential and commercial buildings can perform as a power plant with an energy design concept by integrating renewable energy and energy storage system. However, there has been relatively little focus on how to enhance the residential sector in smart grid development in the context of Thailand. This research focuses on residential buildings only. The technology assessment shows that energy efficiency measures (EEM) must be implemented to reduce the energy demand of the building. The Ice thermal energy storage system (ITES) is an appropriate energy storage system application that can provide cooling energy, which is the major energy consumer in residential building. The integration of EEM, the PV system, and the ITES system can reduce the primary energy demand by 87%, compared to the reference building without comprehensive energy concept design. The power quality assessment shows that the PV hosting capacity is limited up to 75%, which keeps the voltage level in the permissible range. The distributed energy storage system allows the PV prosumer to perform an active role by providing reactive power service to the system at the critical electricity feeder. The economic assessment reveals that the ITES is the most cost-effective investment option, where the battery energy storage (BES) system can become more attractive with incentive support and future cost reduction. The results from the consumer survey reveal that the willingness to pay (WTP) of the EEM and PV system in the detached single-family house is higher than the investment cost, which benefits both consumer and house developer. Technology is a key driver for providing the energy service to the energy system, while consumer behavior and acceptance can increase technology adoption. The Thai government should encourage the residential sector to become a smart user by taking technology, consumer behavior background, and essential energy policy into account.Intelligente Netztechnik, sogenannte Smart Grid-Technologie, kann durch die Einbindung von Informations- und Kommunikationstechnologie die Integration von erneuerbaren Energien in das bestehende Stromnetz verbessern. Wohn- und Gewerbegebäude können mit Hilfe eines Energiekonzepts durch die Integration von erneuerbaren Energien und Energiespeichern als Kleinkraftwerk fungieren. Allerdings gibt es in Thailand bisher wenig Analysen, wie man den Wohnungssektor für die Entwicklung intelligenter Netze nutzbar machen kann. Diese Forschungsarbeit konzentriert sich daher ausschließlich auf Wohngebäude. Die Technologiebewertung zeigt, dass Energieeffizienzmaßnahmen (EEM) umgesetzt werden müssen, um den Energiebedarf der Gebäude zu reduzieren. Ein thermischer Energiespeicher basierend auf Eis (ITES) ist eine geeignete Speicheranwendung, um Kühlenergie bereitzustellen, die der Hauptenergieverbraucher in Wohngebäuden ist. Durch die Integration von EEM, dem PV-System und dem ITES-System kann der Primärenergiebedarf um 87% reduziert werden, verglichen mit einem Referenzgebäude ohne umfassendes Energiekonzept. Die vorliegende Forschungsarbeit zeigt, dass die PV-Aufnahmekapazität auf bis zu 75% ausgeweitet werden kann, ohne dass Spannungsgrenzen verletzt werden. Der dezentrale Energiespeicher ermöglichst es zudem dem PV-Prosumer, durch Blindleistungseinsatz eine aktive Rolle im Stromsystem einzunehmen und Spannungsprobleme in kritischen Leitungssträngen zu reduzieren. Die wirtschaftliche Bewertung zeigt, dass das ITES die kostengünstigste Investitionsoption ist und das Batteriespeichersystem (BES) durch Anreize und künftige Kostensenkungen an Attraktivität gewinnen kann. Die Ergebnisse der durchgeführten Verbraucherbefragung zeigen, dass die Zahlungsbereitschaft für die EEM und das PV-System in Einfamilienhäusern höher ist als die Investitionskosten, was sowohl dem Verbraucher als auch dem Bauherrn des Hauses zugutekommt. Neue Technologien sind zentrale Elemente, um die Bereitstellung von Energiedienstleistungen im Energiesystem zu ermöglichen. Jedoch sind auch Nutzerverhalten und -akzeptanz wichtig, um die Verbreitung der Technologie zu erhöhen. Die thailändische Regierung sollte den Einsatz von Intelligenz im Wohnungssektor fördern und dabei Technologien, Verbraucherverhalten und wesentliche energiepolitische Aspekte berücksichtigen

Transitioning to Affordable and Clean Energy

Transitioning to Affordable and Clean Energy is a collective volume which combines original contributions and review papers that address the question how the transition to clean and affordable energy can be governed. It will cover both general analyses of the governance of transition, including policy instruments, comparative studies of countries or policies, and papers setting out scientifically sound visions of a clean and just energy system. In particular, the following aspects are foregrounded: • Governing the supply and demand side transformation • Geographical and cultural differences and their consequences for the governance of energy transitions • Sustainability and justice related to energy transitions (e.g., approaches for addressing energy poverty) Transitioning to Affordable and Clean Energy is part of MDPI's new Open Access book series Transitioning to Sustainability. With this series, MDPI pursues environmentally and socially relevant research which contributes to efforts toward a sustainable world. Transitioning to Sustainability aims to add to the conversation about regional and global sustainable development according to the 17 SDGs. The book series is intended to reach beyond disciplinary, even academic boundaries

Flexible active power control for PV‐ESS systems:A review

The penetration of solar energy in the modern power system is still increasing with a fast growth rate after long development due to reduced environmental impact and ever-decreasing photovoltaic panel cost. Meanwhile, distribution networks have to deal with a huge amount and frequent fluctuations of power due to the intermittent nature of solar energy, which influences the grid stability and could cause a voltage rise in the low-voltage grid. In order to reduce these fluctuations and ensure a stable and reliable power supply, energy storage systems are introduced, as they can absorb or release energy on demand, which provides more control flexibility for PV systems. At present, storage technologies are still under development and integrated in renewable applications, especially in smart grids, where lowering the cost and enhancing the reliability are the main tasks. This study reviews and discusses several active power control strategies for hybrid PV and energy storage systems that deliver ancillary services for grid support. The technological advancements and developments of energy storage systems in grid-tied PV applications are also reviewed

Grid-Connected Energy Storage Systems: State-of-the-Art and Emerging Technologies

High penetration of renewable energy resources in the power system results in various new challenges for power system operators. One of the promising solutions to sustain the quality and reliability of the power system is the integration of energy storage systems (ESSs). This article investigates the current and emerging trends and technologies for grid-connected ESSs. Different technologies of ESSs categorized as mechanical, electrical, electrochemical, chemical, and thermal are briefly explained. Especially, a detailed review of battery ESSs (BESSs) is provided as they are attracting much attention owing, in part, to the ongoing electrification of transportation. Then, the services that grid-connected ESSs provide to the grid are discussed. Grid connection of the BESSs requires power electronic converters. Therefore, a survey of popular power converter topologies, including transformer-based, transformerless with distributed or common dc-link, and hybrid systems, along with some discussions for implementing advanced grid support functionalities in the BESS control, is presented. Furthermore, the requirements of new standards and grid codes for grid-connected BESSs are reviewed for several countries around the globe. Finally, emerging technologies, including flexible power control of photovoltaic systems, hydrogen, and second-life batteries from electric vehicles, are discussed in this article.This work was supported in part by the Office of Naval Research Global under Grant N62909-19-1-2081, in part by the National Research Foundation of Singapore Investigatorship under Award NRFI2017-08, and in part by the I2001E0069 Industrial Alignment Funding. (Corresponding author: Josep Pou.

Particle Swarm Optimization for Optimal Frequency Response with High Penetration of Photovoltaic and Wind Generation

As the installation of solar-photovoltaic and wind-generation systems continue to grow, the location must be strategically selected to maintain a reliable grid. However, such strategies are commonly subject to system adequacy constraints, while system security constraints (e.g., frequency stability, voltage limits) are vaguely explored. This may lead to inaccuracies in the optimal placement of the renewables, and thus maximum benefits may not be achieved. In this context, this paper proposes an optimization-based mathematical framework to design a robust distributed generation system, able to keep system stability in a desired range under system perturbance. The optimum placement of wind and solar renewable energies that minimizes the impact on system stability in terms of the standard frequency deviation is obtained through particle swarm optimization, which is developed in Python and executed in PowerFactory-DIgSILENT. The results reveal that the proposed approach has the potential to reduce the influence of disturbances, enhancing critical clearance time before frequency collapse and supporting secure power system operation