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Journal Paper Accepted: The need for holistic enterprise control assessment methods for the future electricity grid

The LIINES is happy to announce the publication of the journal article The need for holistic enterprise control assessment methods for the future electricity grid, by Prof. Amro M. Farid (Dartmouth), Bo Jiang (MIT), Aramazd Muzhikyan (Dartmouth), and Prof. Kamal Youcef-Toumi (MIT) in the journal Renewable and Sustainable Energy Reviews.

In this comprehensive literature-based study, the LIINES presents a logical case for integrating power grid assessment methods into a holistic enterprise control framework.  Such a framework is explicitly techno-economic and merges methods power systems engineering and economics.   To support the argument, the LIINES has conducted the most comprehensive review of renewable energy integration studies completed to date.

The paper discusses the need for change in the assessment of the electricity grid as a result of five driving forces.  The driving forces are identified as: decarbonization, growth of electricity demand, transportation electrification, electric power deregulation, and increasing numbers of responsive (“smart”) consumers.  These five drivers require the steadily increasing penetration of solar and wind generation as well as evolving capabilities to support demand side management for the tremendous diversity of loads that connect to the electrical grid.  The integration of these three new grid technologies of renewable energy, electric vehicles, and demand side resources ultimately imposes fundamental changes to the grid’s structure and behavior.

The paper argues that the future electric grid’s needs for reliability, cost efficiency and sustainability necessitates a holistic assessment approach.  Figure 1 shows a guiding structure that leads to five techno-economic control objectives.  This work also uses five lifecycle properties to integrate rather than decompose the engineering design.  The lifecycle properties core to the power grid are dispatchability, flexibility, forecastability, stability, and resilience. The use of these five properties avoids overlap in function of solutions.

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Figure 1: Guiding Structure of Argument

Using such a holistic paradigm for techno-economic assessment, the journal paper conducts the most comprehensive review of renewable energy studies completed to date. It found several limitations to the existing renewable energy integration studies. Firstly, in order to address the holistic nature of the power grid, the real potential of demand side resources needs to be included. Additionally, for power grid balancing, validated simulations rather than statistical methods based on questionable assumptions need to be used.  Furthermore, the consistency between future development of the real market structure and modeling methods needs to be assured. Finally, the investment costs related to the support of the future power grid need to be considered in simulation.

Thus, the paper concludes based on the defined model requirements and the assessment of the current literature, that a framework for holistic power grid enterprise control assessment needs to satisfy the following requirements:

  1. Allows for an evolving mixture of generation and demand as dispatchable energy resources
  2. Allows for an evolving mixture of generation and demand as variable energy resources
  3. Allows for the simultaneous study of transmission and distribution systems
  4. Allows for the time domain simulation of the convolution of relevant grid enterprise control functions
  5. Allows for the time domain simulation of power grid topology reconfiguration in operation time scale
  6. Specifically addresses the holistic dynamic properties of dispatchability, flexibility, forecastability, stability, and resilience
  7. Represents potential changes in enterprise grid control functions and technologies as impacts on these dynamic properties
  8. Accounts for the consequent changes in operating cost and the required investment costs.

These requirements have been realized in a power grid enterprise control simulator that was used for an extensive study of renewable energy integration in the power grid [Link 1], [Link 2].  The simulator includes the physical electrical grid layer and incorporates primary, secondary, and tertiary control functions. This model fits the requirements of the holistic enterprise control method as defined previously.

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 Figure 2: The Enterprise Control Power Grid Simulator

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Journal Paper Accepted at Applied Energy – Demand Side Management in Power Grid Enterprise Control: A Comparison of Industrial & Social Welfare Approaches

The LIINES is happy to announce that our recent paper entitled: Demand Side Management in Power Grid Enterprise Control: A Comparison of Industrial & Social Welfare Approaches, has been accepted to the Applied Energy Journal. This study comes as a result of collaboration between three universities; MIT, Masdar Institute, and Dartmouth. The work is authored by Bo Jiang (MIT), Aramazd Muzhikyan (Masdar Institute), Prof. Amro M. Farid (Dartmouth) and Prof. Kamal Youcef-Toumi (MIT).

Demand response is an integral part of a reliable and cost-effective power grid.  As wind and solar energy become two important power generation sources that reduce CO2 emissions and ensure domestic energy security, their intermittent and uncertain nature poses operational challenges on the electrical grid’s reliability. Instead of relying solely on dispatchable generation, power grid operators, called ISOs, are adopting Demand Response (DR) programs to allow customers to adjust electricity consumption in response to market signals. These DR programs are an efficient way to introduce dispatchable demand side resources that mitigate the variable effects of renewable energy, enhance power grid reliability and reduce electricity costs. Fortunately, the U.S. Supreme Court’s recent ruling Federal Energy Regulatory Commission vs. Electric Power Supply Association, has upheld the implementation of Demand Response allowing its role to mature in the coming years.

Despite the recognized importance and potential of DR, the academic and industrial literature have taken divergent approaches to its implementation. The popular approach in the scientific literature uses the concept of “Transactive Energy” which works much like a stock market of energy; where customers provide bids for a certain quantity of electricity that they wish to consume. Meanwhile industrial implementations (such as those described by FERC order 745) compensate customers according to their load reduction from a predefined electricity consumption baseline that would have occurred without DR. Such a counter-factual baseline may be erroneous. At the LIINES, we have rigorously compared the two approaches. Our previous journal paper published at Applied Energy “Demand side management in a day-ahead wholesale market: A comparison of industrial & social welfare approaches” conducted the comparison in a day-ahead wholesale market context.  It showed, both analytically and numerically, that the use of power consumption baselines in demand response introduces power system imbalances and costlier dispatch.

Our recent paper now expands the analysis from a single day-ahead electricity market to the multiple layers of wholesale markets found in many regions of the North American power grid. This holistic analysis includes the day-ahead, real-time, and ancillary service markets. The integration of these multiple layers of power system operations captures the coupling between them and reveals the the impacts of DR implementation over the course of a full-day with a granularity of tens of seconds. The paper quantifies both the technical and economic impacts of industrial baseline errors in the day-ahead and real-time markets, namely their impacts on power system operating reserve requirements, operating costs and market prices.

The paper concludes that the presence of demand baseline errors – present only in the industrial implementaiton – leads to a cascade of additional system imbalances and costs as compared to the Transactive Energy model. A baseline error introduced in the day-ahead market will increase costs not just in the day-ahead market, but will also introduce a greater net load error residual in the real-time market causing additional costs and imbalances. These imbalances if left unmitigated degrade system reliability or otherwise require costly regulating reserves to achieve the same reliability.

Figure 1: Cascading Cost Increase of Demand Response Baseline Errors in Day-Ahead Energy Market

An additional baseline error introduced in the real-time market further compounds this cascading effect with additional costs in the real-time market, amplified downstream imbalances, and further regulation capacity for its mitigation.

Figure 2: Cascading Cost Increase of Demand Response Baseline Errors in Real-Time Energy Market

Based on these results, the potential for baseline inflation should be given attention by federal energy policy-makers. The effects of industrial baseline errors can be mitigated with effective policy. As a first solution, ISOs could calculate demand response baselines using the same methods of load prediction normally used in energy markets. Such an approach leaves less potential for baseline manipulation. A more comprehensive solution to this problem will be the upcoming trend of transactive energy and would eliminate the concept of baselines and their associated uncertainties entirely.

In depth materials on LIINES smart power grid research can be found on the LIINES website.

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Journal Paper Accepted at IEEE Transactions on Industrial Electronics: An Enterprise Control Assessment Method for Variable Energy Resource Induced Power System Imbalances. Part 2: : Parametric Sensitivity Analysis

We are happy to announce that our recent paper entitled: “An Enterprise Control Assessment Method for Variable Energy Resource Induced Power System Imbalances. Part 2: Parametric Sensitivity Analysis”, has been accepted to IEEE Transaction on Industrial Electronics. The paper is authored by Aramazd Muzhikyan, Prof. Amro M. Farid and Prof. Youcef Kamal-Toumi.

The variable and uncertain nature of the variable energy resources (VER) introduces new challenges to the balancing operations, contributing to the power system imbalances. To assess the impact of VER integration on power system operations, similar statistical methods have been used by renewable energy integration studies. The calculations are based on either the net load variability or the forecast error, and use the experience of power system operations. However, variability and forecast error are two distinguishing factors of VER and both should be taken into consideration when making assessments.

This paper uses the methodology from the prequel to systematically study the VER impact on power system load following, ramping and regulation reserve requirements. While often ignored, the available ramping reserve reflects the generation flexibility and is particularly important in the presence of VER variability. This provides a detailed insight into the mechanisms by which the need for additional reserves emerges. The concept of enterprise control allows studying the impact of power system temporal parameters as well as net load variability and forecast error holistically.

The application of an enterprise control assessment framework allows the empirical identification of the most influential parameters different types of resource requirements. The inclusion of the power system temporal parameters, such as day-ahead market (SCUC) and real-time market (SCED) time steps, is a particularly distinguishing feature of the work. Use of the case-independent methodology allows generalization of the results and prediction of how the system resource requirements change when one of the parameters varies. Moreover, the results reveal the degree of importance of each lever for the power system reliable operations which is crucial for the strategic planning of the grid modernization.

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Journal Paper Accepted at IEEE Transactions on Industrial Electronics: An Enterprise Control Assessment Method for Variable Energy Resource Induced Power System Imbalances. Part 1: Methodology

We are happy to announce that our recent paper entitled: “An Enterprise Control Assessment Method for Variable Energy Resource Induced Power System Imbalances. Part 1: Methodology”, has been accepted to IEEE Transaction on Industrial Electronics. The paper is authored by Aramazd Muzhikyan, Prof. Amro M. Farid and Prof. Youcef Kamal-Toumi.

In recent years, the impact of variable energy resource (VER) integration on power system operations has been studied extensively. While most of the studies agree that VER integration creates a need for additional resources to maintain reliable power system operations, they often fail to give exact assessments due to their methodological limitations. First, a majority of these studies are performed for specific cases and the results obtained cannot be generalized. Moreover, most of these studies are focused on a single control function of power system operations which restricts the scope of the results to that time scale and neglects the coupling between different time scales. Furthermore, most of the results are obtained by statistical calculations, but not validated by numerical simulations. Finally, many of the calculations rely on the experience of system operators which may not necessarily remain valid as the power system continues to evolve.

This newly published paper proposes an enterprise control assessment method for VER integrated power systems. The power system operations are modeled as a three-layer hierarchy. The model integrates resource scheduling, a balancing layer and a regulation layers, which capture most of the balancing operation functionality found in traditional power systems. Such integration allows the study of the coupling between different timescales of power system operations which would be neglected otherwise.

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Another important aspect of this methodology is that integration of power system operation layers also guarantees that the obtained results can be generalized for different cases. To achieve this, some modifications of the traditional power system control actions are performed. The validation of the methodology demonstrates that in the absence of these modifications the simulations lead to unreasonable results for some scenarios.

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Prof. Amro M. Farid presents Power Grid Enterprise Control paper at GCC CIGRE 2013

In recent months, we at the Laboratory for Intelligent Integrated Networks of Engineering Systems have been arguing for “Enterprise Control” in support of the future developments of the electricity grid.  In other words, the power grid’s primary, secondary and tertiary control must be addressed simultaneously to achieve both reliability as well as economic objectives.  These arguments have been presented in various forums.  The most recent of these is an extensive literature review entitled “The Need for Holistic Assessment Methods for the Future Electricity Grid” authored by Prof. Amro M. Farid and Dr. Aramazd Muzhikyan.   Prof. Farid presented this work at the 2013 GCC CIGRE conference held in Abu Dhabi on November 18-20.

Full text of the paper and related work may be found through the LIINES Website  under paper code [EWN-C08] :  http://amfarid.scripts.mit.edu publications page.


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IEEE Spectrum Features LIINES Research on Power Grid Enterprise Control Systems

Following the recent publication of the 2013 September Edition of the IEEE Smart Grid Newsletter where Prof. Amro M. Farid advocates the concept of power grid enterprise control, the IEEE Spectrum Magazine has also promoted the concept amongst its readership.  There, Bill Sweet discusses Power Grid Enterprise Control in the context of “Completely Self-Controlled Power Systems“.

Further publication on the topic can be found on the LIINES Website under the Smart Power Grids research page.

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LIINES Research on Power Grid Enterprise Control Systems Featured in IEEE Smart Grid Newsletter

Since the inception of LIINES, research in smart power grids has been a fundamental theme.  One important concept advocated by this work is power grid enterprise control; where the multiple layers of power operations and control are assessed and designed not just individually but together in a holistic fashion.  In the 2013 September Edition of the IEEE Smart Grid Newsletter, Prof. Amro M. Farid continues his advocacy of Power Grid Enterprise control.

Further publication on the topic can be found on the LIINES Website under the Smart Power Grids research page.

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Journal Paper Accepted at Springer’s Intelligent Industrial Systems Journal: Multi-Agent System Design Principles for Resilient Coordination & Control of Future Power Systems

The LIINES is pleased to announce the acceptance of the paper: “Multi-Agent System Design Principles for Resilient Coordination & Control of Future Power Systems” in Springer’s Intelligent Industrial Systems Journal. The paper is authored by Amro M. Farid and was published online at May 28th 2015.

Recently, the vision of academia and industry has converged, defining future power system as intelligent, responsive, dynamic, adaptive, and flexible. This vision emphasizes the importance of resilience as a “smart grid” property. It’s implementation remains as a cyber-physical grand challenge.

Power grid resilience allows healthy regions to continue normal operation while disrupted or perturbed regions bring themselves back to normal operation. Previous literature has sought to achieve resilience with microgrids capable of islanded operation enabled by distributed renewable energy resources. These two factors require a holistic approach to managing a power system’s complex dynamics. In our recent work (e.g. link 1 and link 2), we have proposed as means of integrating a power system’s multiple layers of control into a single hierarchical control structure.

In addition to enterprise control, it is important to recognize that resilience requires controllers to be available even if parts of the power grid are disrupted. Therefore, distributed control systems, and more specifically Multi-Agent Systems have often been proposed as the key technology for implementing resilient control systems. Multi-agent systems are commonly used to distribute a specific decision-making algorithm such as those in market negotiation and stability control. However, very few have sought to apply multi-agent systems to achieve a resilient power system.

The purpose of the paper entitled “Multi-Agent System Design Principles for Resilient Coordination & Control of Future Power Systems” is two fold. First, it seeks to identify a set of Multi-Agent System design principles for resilient coordination and control. Second, the paper assesses the adherence of existing Multi-Agent System implementations in the literature with respect to those design principles.

The set of design principles is based on newly developed resilience measures for Large Flexible Engineering Systems. These measures use Axiomatic Design and are directly applicable to the power grid’s many types of functions and its changing structure. These design principles, when followed, guide the conception of a multi-agent system architecture to achieve greater resilience.

About the author: Wester C.H. Schoonenberg completed his B.Sc. in Systems Engineering and Policy Analysis Management at Delft University of Technology in 2014. After his bachelors’ degree, Wester started his graduate work for the LIINES at Masdar Institute, which he continues as a doctoral student at Thayer School of Engineering at Dartmouth College in 2015. Currently, Wester is working on the integrated operation of electrical grids and production systems with a special interest in Zero Carbon Emission Manufacturing Systems.

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LIINES Website: http://amfarid.scripts.mit.edu

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Journal Paper Accepted: Relative Merits of Load Following Reserves & Energy Storage Market Integration Towards Power System Imbalances

We are happy to announce that our recent paper entitled: “Relative Merits of Load Following Reserves & Energy Storage Market Integration Towards Power System Imbalances”, has been published in the International Journal of Electrical Power & Energy Systems (IJEPES). This study comes as a result of collaboration between three universities; Masdar Institute, Dartmouth, and MIT. The work is authored by Aramazd Muzhikyan (Masdar Institute), Prof. Amro M. Farid (Dartmouth) and Prof. Kamal Youcef-Toumi (MIT).

The existing energy storage resource (ESR) studies bound their discussion to a single timescale of power system operations, such as day-ahead scheduling or real-time balancing. As a result, these studies are only able to capture the impact of the ESR integration on the associated timescale, while any effects that may span across adjacent timescales are omitted. Recently, power grid enterprise control has been developed that integrates different timescales of balancing operations into a multi-layer control hierarchy. The benefits of such holistic power system modeling have been demonstrated for studies on renewable energy integration, the determination of the power system imbalances and the assessment of reserve requirements.

This paper integrates ESRs into the power system enterprise control for the first time. While the ESR integration is expected to mainly affect its associated timescale, such methodology also allows capturing the potential impact on adjacent timescales. If such coupling of timescales exists, it can be exploited to reduce the system resource requirements. This methodology is also used to demonstrate the differences in imbalance mitigation performance of ESRs and load following reserves. While both these resources can be used for balancing the system, the enterprise control methodology unveils their differences and relative merits for different balancing scenarios. The notion of ‘‘utilization efficiency’’ of a given resource is introduced here which is defined as the amount of that resource required to mitigate 1MW of imbalance.

A novel ESR scheduling method has also been developed in this paper that beneficially exploits the coupling between different timescales. Since the day-ahead market has hourly time step, the obtained generation schedule has a stair-like profile with constant values for each hourly interval. However, such stair-like profile does not capture the intra-hour variations of the demand, leading to higher load following reserve requirement. Taking advantage of the timescale coupling, a sub-hourly ESR profile is designed based on the day-ahead market output that, in addition to the traditional benefits of shaving the peak load and reducing the operating cost, also simultaneously reduces the load following reserves requirement. The newly designed ESR schedule is based on piecewise linear harmonic functions and resembles the smooth demand profile within hourly intervals.

The results show that the ESR and the load following reserves have different performances and are better suited for applications in different circumstances. While the utilization efficiency is nearly constant for the load following reserves, the performance of the ESR significantly depends on the temporal characteristics, namely the net load variability and the day-ahead market time step. Higher variability and smaller day-ahead market time step result in better ESR utilization efficiency. The results also show that the generation schedule of the system without ESR has a stair-like form, while the total generation+ESR schedule of the system with ESR integration has a much smoother form and more closely resembles the actual demand profile. This difference defines the actual load following reserve requirement for each system. The results show that the load following reserve requirement of the system with ESR integration is significantly lower compared to the traditional system without ESR.

 

The comparison of the schedules for a system without ESR and a system with ESR scheduled according to the proposed method

The difference of load following reserve requirements for systems without and with ESR.

In depth materials on LIINES smart power grid research can be found on the LIINES website.

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Prof. Amro M. Farid contributes to World Wind Energy Association Report

The World Wind Energy Association (WWEA) technical committee has recently published a report entitled “Wind Energy 2050: On the shape of near 100% RE grid”, which studies the challenges of wind energy integration into the power grid and discusses some of the solutions to address these challenges. Chapters 5 and 6 of this report are based upon the work of Dr. Amro M. Farid and discuss the evolution the power grid as it accommodates increasing capacities of wind energy.

Wind and solar energy have already become mainstream energy sources in some regions of the world. While the integration of wind energy has numerous benefits, it also creates new challenges for power system operations. Wind energy is inherently variable and, in order to successfully accommodate it, the power system has to undergo a dramatic change.   Furthermore, and in contrast to the traditional thermal generation units, wind energy sources are non-dispatchable in the traditional sense, meaning their outputs cannot be set to the desired value. As a result, the integration of wind energy requires new approaches to power grid planning and management, including investments into improved wind forecasting techniques and reconsidering operating reserve requirements.

A conventional power system consists of relatively few centralized and dispatchable generation units, and a large number of distributed and stochastic (but accurately forecastable) loads. The electricity is delivered from the centralized and predominantly thermal power plants to the distributed electrical loads. During many decades of operations, power system operators and utilities have developed improved methods for performing their tasks. Generation scheduling and dispatch, reserve management and control technologies have matured. Load forecasting accuracy has improved significantly, reducing forecast errors to as low as a few percent. Power system security and reliability standards have also evolved accordingly.

Six key drivers currently govern the evolution of the grid, namely environment protection, reliability concerns, renewable energy integration, transportation electrification, consumer participation and power market deregulation. This evolution will lead to a diversification of the power grid energy portfolio to include more solar, wind, energy storage and demand-side resources. Thus, the newly emerging operation procedures will not only engage with generators but also with consumers and other ancillary units. As a result, the already existing control technologies and procedures will expand significantly in both number and type.  This will challenge the basic assumptions of power system design and operations. Therefore, the question is not how to mitigate wind variability, but rather how the power grid should evolve to successfully accommodate a high penetration of wind energy.

Governed by these drivers, power system generation and consumption will evolve towards more equal roles in grid operations.  First, from the perspective of dispatchability, wind energy sources resemble traditional consumption in that they are non-dispatchable and forecasted. On the other hand, the introduction of demand response creates makes some portion of the energy consumption dispatchable much like traditional power generation facilities. These two trends change the balance of dispatchability and forecastability as shown in Table 1. Second, the integration of wind energy, like most renewable energy sources, changes the spatial distribution of the generation. Wind energy sources can vary from several kWs to hundreds of MWs.  While larger facilities will continue to be installed centrally into the transmission system, the smaller facilities will be installed at the power grid periphery as distributed generation.  (See Figure 2).  This creates the potential for upstream flow in the distribution system, which was not generally allowed before, and requires the redesign of the protection system accordingly.

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Table 1: Future grid generation and demand portfolio

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Figure 2: Graphic representation of the evolving power grid structure

While many power grid phenomena overlap, the literature has traditionally treated them strictly separately. The evolution of the power grid necessitates reconsidering the distinction between  timescales.   It also requires revisiting the distinction between the transmission and distribution systems. In advocating for power grid enterprise control, our work encourages holistic approaches that work across time scales as well as the fully supply chain of electricity including both the transmission as well as the distribution system.

This work also moves away from the traditional classification of technical and economic control objectives and utilizes the concept of integrated enterprise control as a strategy for enabling holistic techno-economic performance of wind integration. As shown in Figure 3, the power system is modeled as a cyber-physical system, where the physical integration of wind energy and demand-side resources must be assessed in the context of the control, automation, and information technologies. The horizontal axis represents the energy value chain from the generation to the consumption. Finally, the third axis classifies both the generation and the consumption into dispatchable as well as stochastic units. This graph represents the scope of the power system that must address a complex mix of technological, system and societal objectives.

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Figure 3: Electrical power grid as a cyber-physical system

This work also moves away from the traditional classification of technical and economic control objectives and utilizes the concept of integrated enterprise control as a strategy for enabling holistic techno-economic performance of wind integration. As shown in Figure 3, the power system is modeled as a cyber-physical system, where the physical integration of wind energy and demand-side resources must be assessed in the context of the control, automation, and information technologies. The horizontal axis represents the energy value chain from the generation to the consumption. Finally, the third axis classifies both the generation and the consumption into dispatchable as well as stochastic units. This graph represents the scope of the power system that must address a complex mix of technological, system and societal objectives.

In depth materials on LIINES smart power grid research can be found on the LIINES website.

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