Multiattribute value function for the assessment of distributed generation projects: Application to technical criteria

Impact of increasing transmission capacity for a massive integration of renewable energy on the energy and environmental value of distributed generation

This paper reports the results from a survey conducted in 2010/2011 among 14 Norwegian distribution system operators (DSOs) concerning their experiences with integration of distributed generation (DG) in distribution networks. The survey shows what kind of problems DSOs experience caused by DG connected to their networks, how the DSOs approach the problems and what kind of planning methodologies and tools the DSOs are using to overcome the problems. The results of the survey show that most of the DSOs have experienced problems with DG units connected to their network, despite the network reinforcements that have been necessary to integrate many of the DG units. The survey also shows that several of the DSOs are expecting a considerable increase in the number of DG units in their distribution networks in the years to come. This increase will probably be accelerated by the introduction of green certificates by 01.01.2012[1], which is expected to increase the profitability of many DG projects. Some of the DSOs have started to address the challenges in their planning methodologies, improving their planning procedures in order to optimize the DG integration process and decrease the need of expensive grid reinforcements. Still, only a few go beyond the normal planning procedures for networks without DG.

Interconnect protection allows DG to operate in parallel with the utility power system and is the single most important technical issue in most DG projects. Typically, protection requirements to connect distributed generators to the utility grid had been established by each utility. These guidelines generally cover smaller distributed generators (10 MW or less), which are usually connected to the utility system at the subtransmission and distribution level. These utility circuits are designed to supply radial loads. Thus, the introduction of generation provides a source for redistribution of the fault current on the feeder circuit, which can cause the loss of relay coordination and potential overvoltages. Within the past few years, there have been efforts by the IEEE, as well as individual states, to develop standards and guidelines for the interconnection of DG. The stated goal of these standards/guidelines is to have a single document of standard technical requirements for DG interconnection rather than having to conform to local utility practices and guidelines. This paper examines how well this objective has been met.

This paper proposes a new approach to determine a distribution network usage fee (DUF) for distributed generators. The methodology is based on distribution of costs associated with use of the distribution network, among all system users, including those with or without distributed generation (DG). To estimate the distribution network costs, impact of DG on the distribution network is valued. In order to achieve a fair and equitable electricity tariff, this methodology considers DUF calculation on the following DG variables: type (photovoltaic or wind), location, and size. Uncertainty associated with system demand and energy resources is probabilistically modeled through their cumulative probability functions. The proposed method is tested on a 33-node distribution system, under scenarios of variable location and capacity of the DG system. Furthermore, internal rate of return is calculated to evaluate DUF application on DG projects.

A New Mexico statute allows investor-owned utilities to recover costs of “standby and ancillary services” resulting from distributed generation (DG). In attempting to do so, it is important to recognize both the physical and economic impacts, positive and negative, that distributed generation creates. Distributed generation has different impacts on ancillary and standby services depending on the location, capacity, and production patterns of the systems. Low penetrations of small distributed generation systems will not create significant contingencies for utilities. System impact of fluctuations in DG production may be no larger than normal fluctuations caused by customer demand, such as an air conditioner cycling. Higher penetrations and large DG system may produce noticeable impacts; so magnitude is critical when determining potential additional recoverable utility costs. Understanding DG impact on ancillary services is a relatively new and emerging area of study and as such there are not well-established formulas or protocols. Discretion is required. A hosting capacity analysis can help determine how much DG can be implemented before the impacts become substantive. Standby rates are traditionally used for large industrial generators or combined heat and power systems and threshold system size levels are often used in determining applicability of standby rates. System size thresholds may also be appropriate for standby rates and DG. Relatively small, geographically diverse DG systems are unlikely to create a noticeable coincident outage, so developing a standby charge based on assumed coincidence may not be appropriate. Individual lines and feeders may have considerable excess capacity during coincident outages, or they may be fully utilized and facing upgrades in the near future, which could vary over time. Understanding specific events that create concern for utilities is critical to developing an appropriate rate mechanism (e.g., single residential or community system outage, cascading event, clouds, eclipse). Any modeling or studies of the grid should also recognize the unique situation created when DG is coupled with a smart inverter or storage. These devices change the value proposition and can help mitigate some of the voltage and ramping issues DG can pose for a utility. Utilities can recover their fixed costs in a variety of ways, and some are better suited for DG than others. Beyond charging for standby and ancillary services, other options include fixed customer charges, demand charges, minimum bills, time-of-use rates and updated net energy-metering policies. Studies and analyses of the specific impacts that DG has on the grid should inform utilities’ decision-making process because distributed generation creates both costs and benefits for the grid. Any charge specific to DG customers should be backed up with analysis. At the heart of this conversation is utilities attempting to recover fixed costs. Allowing utilities to indiscriminately recover all stranded fixed costs can negatively affect long-term market efficiency by blunting utility incentives to lower costs and acting as a barrier to entry and exit. The current status of New Mexico’s grid, impending infrastructure updates, and likely customer adoption patterns for DG (backed up by transparent analysis) should remain at the forefront when considering charges for standby and ancillary services. Recognizing that utility regulation is largely a reactive process, it is recommended that applications for DG related standby or ancillary services cost recovery mechanisms be thoroughly reviewed by an experienced economist. If the commission has no such skill set on staff, one might be hired.

Distributed generation (DG) units are increasing in number all over the world, thus providing new opportunities, but also challenges for distribution system operators. This paper briefly describes the status for integration of DG in Norway, highlighting challenges that Norwegian distribution network companies are facing with regard to large scale integration of DG, typically small scale hydro. The paper further reports from a survey describing some aspects of DG integration and existing planning methodologies among distribution network companies. An overall methodology for planning of integration of DG is presented, highlighting different aspects of inherent uncertainty in the planning process. The methodology can be used by the distribution system operators to develop long term network plans taking into consideration the local potential for DG, but also the uncertainty (in terms of timing, location and capacity) for DG development.

With the ongoing expansion and interconnection of electrical power systems, alongside the rapid proliferation of renewable distributed generations (DGs), the short-circuit extent in the power grid is experiencing a significant rise. Fault current limiters (FCLs) have been introduced in an effort to address this issue, ensuring the robustness and sustainability of expensive power system components when confronted with short-circuit faults. Among the various types of FCLs, bridge-type DC reactor fault current limiters (BDCR-FCLs) have emerged as one of the most promising options. While BDCR-FCLs have shown excellent properties in limiting harmful short-circuit currents, they are also advantageous in other respects. This paper investigates the supplementary functionalities of BDCR-FCLs as a multifaceted device towards the enhancement of the quality of supplied energy in terms of total harmonic distortion (THD) reduction, power factor (PF) correction, peak current reduction for nonlinear loads, and soft load variation effects, as well as their capability to limit fault current. To this aim, the capabilities of BDCR-FCLs have been studied through various simulated case studies in PSCAD/EMTDC software V5.0.1, in addition to experimental tests considering an AC microgrid connected to a DC system. The experimental and simulation investigations verify the superior multifaceted functionalities BDCR-FCLs introduce in addition to their excellent fault current-limiting capabilities. The results show that PF improved by 6.7% and 7%, respectively, in simulation and experimental tests. Furthermore, the current THD decreased by 20% and 18% in the simulation and experiment, respectively.

Significant distributed generation (DG) will be connected to distribution systems. As a result, the integration of this generation may change the assumptions under which the systems were designed and results in the operation situations that do not occur in a conventional system without directly connected distributed generation. Careful engineering planning for DG penetration is therefore needed. Understanding the issues related to the DG integration is required to maintain the reliability and proper operation performance of the system. Proper knowledge and engineering can result in effective DG integration in distribution systems. This paper presents the results of a project recently performed by the power company, Vattenfall, in Sweden. The project investigates potential advantages related to DG integration, and performed a series of reliability simulations to analyze how the DG integration affects the system reliability. The results of the project indicate that DG can be utilized to improve the system reliability and reduce not supplied energy. The project shows that various factors can influence the benefits of DG integration. It is of great value to take into account these influencing factors and incorporate DG into the planning process to obtain the most beneficial solution of DG penetration. The details of the reliability simulations are addressed and discussed in the paper.

The integration of Distributed Generation (DG) in electric power systems has brought about the need for the improvement of the existing protective relaying principles used in distribution systems. This is because the integration of DG transforms the conventional single-source radial distribution system to a bidirectional multisource distribution system. Therefore, it is necessary to analyse the new short circuit fault current level, the general requirements for the integration of DG units, the requirement under abnormal conditions, power quality requirements, and the protection requirements. This chapter presents the impact of DG units on the short circuit current level and protective relaying in distribution systems. An overview of protection in conventional distribution system is first described. Afterwards, the impact of DG on the short circuit fault current and the protection of a distribution system integrated with DG are presented. Also, case studies and simulation examples on protective relaying in a distribution system integrated with DG are presented. Furthermore, some emerging technologies that can be applied to improve the protective relaying schemes in a DG-integrated distribution system are highlighted.

Over the past 10 years, the use of distributed generation (DG) has become one of the important directions in the development of the electric power industry in many countries across the world. According to its purpose, DG is used to supply remote electricity consumers. In conditions of market uncertainty in the development of the energy sector, one of the most profitable solutions for increasing the reliability of consumer power supply is to install a small-scale generation near the distant loads. Under such option the risks of energy shortage and loss of power supply from power source of the main network are reduced, reliability of power supply is improved, the energy quality parameters are improved, power and energy losses are reduced. However, the growth of the DG penetration in electric power systems (EPS) has not only positive aspects, but also creates certain technical problems that are associated with fluctuations of EPS parameters as well as with DG controllability under normal and emergency conditions. These problems can be solved but at the cost of more complex EPS dispatch and automatic control. The solution requires new mathematical models to substantiate the development of EPS and power supply systems, to analyze and to manage their state. In this article the authors propose a novel mathematical model for DG planning and optimization basing on integral quality criterion that incorporates power supply quality and reliability.

The modern power systems have recently increased the interest in distributed generation (DG) technologies due to, fuel cost uncertainties, environmental constraints, and increasing power consumption with shortage of transmission capacities. Distributed generation (DG) using clean and renewable energy in power supply system have attracted serious attention. Many developing countries are adopting distributed generation (DG) technologies for their power systems expansion planning. Solar Energy is one of the most promising, nonpolluting, free source of energy. Libya is a developing country located in North Africa, most of the country’s land area is desert which is wealthy in solar radiation income, found to be one of the most reliable and consistent solar energy resources. Despite of this energy resource this area (southern part) of Libya experiences permanent outages which may last for days in certain occasions. This paper investigates the implementation of distributed generation using solar energy resource to improve security of supply to these areas and emphasizes other benefits on power quality and economics.

Chapter 9 - Distributed generation in deregulated energy markets and probabilistic hosting capacity decision-making challenges

The Distributed Generation (DG) or dispersed generation including small size conventional and renewable type of energy sources has gained a great interest in distribution system planning. The integration of DGs into distribution systems achieves numerous technical, economical and environmental benefits and becomes an attractive alternative by future expansion planning of the distribution network. In order to maximize these benefits, it is very important to optimally determine the site and size of the DG units under different operation conditions. This paper presents a two stage methodology for optimal siting and sizing of DGs in medium voltage network. In the first stage, DG placement is selected to reduce the real power losses of the system and to improve its voltage profile. The size of the DG units is determined in the second stage using sequential quadratic programming technique to minimize the total investment and operation cost of the system. The proposed method is tested on real 42 bus test distribution system and the results are presented.

Nowadays, Distributed Generation (DG) has become more popular as a viable element of electric power systems. DG was designed as a small scale generation sources in order to locate at or near load center. The installation of DG is usually deployed within the distribution system to get the positive impacts such as reducing power losses, enhancing voltage profiles, differing costly for upgrading process, and reducing transmission and distribution network congestion. The purpose of this paper is to present a new technique namely Adaptive Embedded Clonal Evolutionary Programming (AECEP). The objective of the study is to employ AECEP optimization technique for loss minimization and voltage profile monitoring. This technique was developed to optimally determine the location and sizing of DG for the same purpose. Test was performed on the IEEE 69-Bus RDS for several cases in terms of loading conditions. The proposed AECEP was implemented for single DG and two DGs installation. The result of the proposed AECEP technique was found in a good agreement with those obtained from the EP and AIS in terms of loss minimization and voltage profile improvement.

Distributed generation (DG) has changed the energy landscape by increasing system reliability and decreasing environmental impacts through its incorporation into electrical power systems. The additional complexity brought forth by DG, however, also calls for the creation of more precise and effective fault finding techniques. This abstract explores current developments in fault localization strategies for DG-integrated electrical power systems using deep learning (DL) methods. Due to the non-linear, dynamic, and ever-changing nature of DG-rich networks, traditional fault finding algorithms generally struggle to correctly locate faults in these networks. Deep learning's potential as a solution may be seen in its capacity to recognise complex patterns and adjust to new information. Specifically, this study looks into how DL models like CNNs and RNNs can be used to improve the precision with which faults can be detected and localised in DG-integrated power systems. The creation of DL-based fault location algorithms that use high-resolution data from different sensors like smart metres and phasor measurement units (PMUs) is a major advancement. These algorithms draw on the temporal and spatial information available in power system data to pinpoint the exact location of malfunctions. Additionally, the study looks into the stability and transferability of DL models using various DG technologies and setups. Pre-trained models are transferred learning approaches to guarantee adaptability and reliability across a wide range of DG applications. The findings show that in DG-rich contexts, fault location algorithms based on DL perform much better than their conventional counterparts. These developments have the potential to strengthen electrical grids, reduce the frequency and duration of outages, and improve the reliability of today's power systems. The incorporation of deep learning into fault location algorithms is an important step towards building a more dependable and robust power system, especially as DG integration continues to grow