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This article proposes a transmission-system-level aggregated model of Battery Energy Storage Systems (BESSs) distributed through Active Distribution Networks (ADNs), to study the dynamic performance and services provided by these systems to power grids. ADNs comprise intelligent loads, local generation, particularly solar PV, and BESSs, which can provide different services to transmission grids, including voltage control, oscillation damping, frequency regulation, and active and reactive power injections. Proper equivalent models of the ADN components allow to evaluate the impact and integration of these networks on power grids. In this article, ADN’s measurements of the aggregated response of the BESSs at the boundary bus with the transmission system are used to develop an aggregated black-box model based on two Neural Networks (NNs), one for active power and another for reactive power, with their optimal topology obtained using a Genetic Algorithm (GA). Detailed simulations are performed, using a commercial-grade software for power system analysis, of multiple BESSs connected to a CIGRE benchmark ADN connected to a bus of the 9-bus WSCC benchmark transmission network; the test ADN is then replaced by the proposed black-box model, with aggregated models of the loads and PV generation, demonstrating that the proposed model can accurately reproduce the results obtained. [ABSTRACT FROM AUTHOR]

This paper discusses the implementation of a transient stability model of Compressed Air Energy Storage (CAES) systems in a power system analysis package. A block-diagram based model of a two-machine CAES system is proposed, including specific controls for active power, reactive power, and State of Charge (SoC), which consider limits associated with the cavern pressure. As an application, the model is implemented in Powertech's TSAT software connected to the 9-bus WSCC benchmark power system, which is then used to study the impact of a CAES facility in the transient and frequency stability of the system. Several contingencies are simulated comparing the CAES performance to a gas turbine and a base-case without storage, demonstrating that the CAES system improves the system transient stability due to its charging stage, controls, and additional inertia. Finally, the CAES model is used to study the effects of cavern sizes in the frequency of the system. It is shown that CAES systems have certain special characteristics that make them attractive as a storage technology to provide stability and regulation services, besides their energy arbitrage capabilities. [ABSTRACT FROM AUTHOR]

This paper presents practical energy management system (EMS) models which consider the operational constraints of distributed energy resources, active-reactive power balance, unbalanced system configuration and loading, and voltage dependent loads. A novel linearization approach is proposed and validated based on the fact that, for isolated microgrids, due to the characteristics of feeders, network losses, and voltage drops across feeders are relatively small. The proposed EMS models are mixed integer quadratic programming problems, requiring less computation time and thus suitable for online applications. The practical EMS models are compared with a typical decoupled unit commitment and optimal power flow-based EMS with and without consideration of system unbalancing. The models, along with “standard” EMS models, are tested, validated, and compared using a CIGRE medium voltage benchmark system and the real isolated microgrid of Kasabonika Lake First Nation in Northern Ontario, Canada. The presented results demonstrate the effectiveness and practicability of the proposed models. [ABSTRACT FROM AUTHOR]

Electric power systems are facing major challenges because of the increase in penetration of energy resources (ERs). This paper focuses on composite system reliability based planning for ERs, and presents novel clustering techniques based approaches to determine the optimal location, size and year of installation of ERs in the system. The K-means clustering and Fuzzy C-means clustering techniques are applied to the set of reliability indices, Load Not Served per Interruption (LNSI), which are determined using nodal minimal cut sets. The nodal minimal cut sets are obtained using an optimal power flow (OPF) based approach in this paper. Once the optimal sizes and locations of ERs are obtained, the earliest year of penetration is determined using an adequacy check algorithm. Detailed studies presented considering the IEEE RTS demonstrate the applicability of the proposed technique. [ABSTRACT FROM PUBLISHER]

This paper presents a novel framework for planning and investment studies pertaining to the implementation of system-wide conservation voltage reduction (CVR). In the CVR paradigm, optimal voltage profiles at the load buses are determined so as to yield load reductions and hence energy conservation. The system modifications required to operate at such voltages is known to be capital intensive, which is not desirable by investors. Hence, the proposed model determines the system savings and the appropriate price incentives to offer industries such that a minimum acceptable rate of return is accrued. In this model, the industrial facilities are represented by a combination of constant impedance, constant current, and constant power loads. A detailed case study for Ontario, Canada, is carried out considering that industrial loads are investing in voltage optimization to reduce their energy costs. The optimal incentives that need to be offered by the system planner, over a long-term horizon, and across various zones of Ontario, are determined using the presented mathematical model. Furthermore, a comprehensive risk analysis comprising sensitivity studies and Monte Carlo simulations is carried out considering the variations in the most uncertain model parameters. [ABSTRACT FROM PUBLISHER]

This paper presents a new modeling framework for analysis of impact and scheduling of price-responsive as well as controllable loads in a three-phase unbalanced distribution system. The price-responsive loads are assumed to be linearly or exponentially dependent on price, i.e., demand reduces as price increases and vice versa. The effect of such uncontrolled price-responsive loads on the distribution feeder is studied as customers seek to reduce their energy cost. Secondly, a novel constant energy load model, which is controllable by the local distribution company (LDC), is proposed in this paper. A controllable load is one that can be scheduled by the LDC through remote signals, demand response programs, or customer-end home energy management systems. Minimization of cost of energy drawn by LDC, feeder losses, and customers cost pertaining to the controllable component of the load are considered as objectives from the LDCs and customers’ perspective. The effect of a peak demand constraint on the controllability of the load is further examined. The proposed models are tested on two feeders: 1) the IEEE 13-node test feeder; and 2) a practical LDC feeder system. Detailed studies examine the operational aspects of price-responsive and controllable loads on the overall system. It is observed that the LDC controlled load model results in a more uniform system load profile, and that with a reduction in the peak demand cap, the energy drawn decreases, consequently reducing feeder losses and LDC’s and customers’ costs. [ABSTRACT FROM PUBLISHER]

An affine arithmetic (AA) method is proposed in this paper to solve the optimal power flow (OPF) problem with uncertain generation sources. In the AA-based OPF problem, all the state and control variables are treated in affine form, comprising a center value and the corresponding noise magnitudes, to represent forecast, model error, and other sources of uncertainty without the need to assume a probability density function (pdf). The proposed AA-based OPF problem is used to determine the operating margins of the thermal generators in systems with uncertain wind and solar generation dispatch. The AA-based approach is benchmarked against Monte Carlo simulation (MCS) intervals in order to determine its effectiveness. The proposed technique is tested and demonstrated on the IEEE 30-bus system and also a real 1211-bus European system. [ABSTRACT FROM AUTHOR]

This paper presents a novel modeling framework for the analysis of Plug-in Electric Vehicle (PEV) charging in unbalanced, residential, distribution systems. A Smart Distribution Power Flow (SDPF) framework is proposed to determine the controlled or smart charging schedules and hence address the shortcomings of uncontrolled charging. The effect of peak-demand constraint imposed by the Local Distribution Company (LDC) is also studied within the SDPF framework for the smart charging scenarios. Uncontrolled versus smart charging schemes are compared for various scenarios, from both the customer's and the LDC's perspective. Various objective functions, such as energy drawn by the LDC, total feeder losses, total cost of energy drawn by LDC and total cost of PEV charging are considered. Studies are carried out considering two sample systems i.e., the IEEE 13-node test feeder and a real distribution feeder. Analyses are also presented considering a probabilistic representation of the initial state of charge (SOC) and start time of charging for various scenarios to take into account the difference in customers' driving patterns. The results show that uncontrolled charging of PEVs results in increased peak demand, low node voltage levels, and increased feeder current magnitudes. On the other hand, the SDPF framework provides very satisfactory operating schedules for the overall system including smart PEV charging. [ABSTRACT FROM PUBLISHER]

This paper presents a novel method based on affine arithmetic (AA) for voltage stability assessment of power systems considering uncertainties associated with operating conditions, which may be attributed to intermittent generation sources, such as wind and solar. The proposed AA-based method reduces the computational burden as compared to Monte Carlo (MC) simulations, and also improves the accuracy as compared to some analytical approaches. The proposed method is tested using two study cases: first, a 5-bus test system is used to illustrate the proposed technique in detail, and thereafter a 2383-bus test system to demonstrate its practical application. The results are compared with those obtained using MC simulations to verify the accuracy and computational burden of the proposed AA-based method, and also with respect to a previously proposed technique to estimate parameter sensitivities in voltage stability assessment. [ABSTRACT FROM PUBLISHER]

This paper presents a novel probabilistic distribution load flow (PDLF) algorithm to study the effect of connecting a wind turbine (WT) to a distribution system. This probabilistic approach is used to capture the stochastic behavior of the generation of WTs. Three different models of WTs are developed to be embedded in the PDLF. Consequently, a probabilistic approach to evaluate the impact of wind penetration into distribution systems is developed. Futhermore, the effect of WT penetration on feeder losses, voltage profile and substation powers is presented. [ABSTRACT FROM PUBLISHER]

This paper presents a novel framework based on range arithmetic for solving power flow problems whose input data are specified within real compact intervals. Reliable interval bounds are computed for the power flow problem, which is represented as an optimization model with complementary constraints to properly represent generator bus voltage controls, including reactive power limits and voltage recovery processes. It is demonstrated that the lower and upper bounds of the power flow solutions can be obtained by solving two determinate optimization problems. Several numerical results are presented and discussed, demonstrating the effectiveness of the proposed methodology and comparing it to a previously proposed affine arithmetic based solution approach. [ABSTRACT FROM PUBLISHER]

This paper presents a new paradigm for distribution system operation in the presence of distributed generation (DG) sources taking into consideration the goodness factor of the DG units. The proposed concept of goodness factor of DG units is based on the computation of the incremental contribution of a DG unit to distribution system losses. The incremental contributions of a DG unit to active and reactive power losses in the distribution system are termed as the active/reactive incremental loss indices (ILI). The goodness factors are integrated directly into the distribution system operations model, which is based on an optimal power flow (OPF) framework. This model seeks to minimize the distribution company's (disco's) energy costs in the short term taking into account the contribution (goodness factor) of each DG unit. Two scenarios are considered in the paper: the first scenario considers the disco to be the owner of the DG units and hence is responsible for their scheduling and dispatch, and the second scenario considers the DG units to be investor-owned. The analysis was carried out considering an 18-bus distribution network extracted from the well-known IEEE 30-bus system and a 69-bus distribution system. [ABSTRACT FROM AUTHOR]

This paper examines the possibility of providing reactive power support to the grid from wind farms (WFs) as a part of the ancillary service provisions. Detailed analysis of the WF capability curve is carried out considering maximum hourly variation of wind power from the forecasted value. Different cost components are identified, and subsequently, a generalized reactive power cost model is developed for wind turbine generators that can help the independent system operator (ISO) in managing the system and the grid efficiently. Apart from the fixed cost and the cost of loss components, a new method is proposed to calculate the opportunity cost component for a WF considering hourly wind variations. The Cigré 32-bus test system is used to demonstrate a case study showing the implementation of the developed model in short-term system operations. A finding is that higher wind speed prediction errors (a site with high degree of wind fluctuations) may lead to increased payments to the WFs for this service, mainly due to the increased lost opportunity cost (LOC) component. In a demonstrated case, it is found that 2340 $/h is paid to the WF as the LOC payment only, when the wind prediction error is 0.5 per unit (p.u.), whereas 54 $/h is the expected total payment to the WF when the prediction error is 0.2 p.u. for its reactive power service. [ABSTRACT FROM AUTHOR]

The need for a market based approach for reactive power procurement has been recognized by FERC. Due to the localized characteristic of reactive power, regulatory mechanisms are necessary to mitigate the possibility of holding market power by generators. The regulator is responsible for devising the regulatory mechanisms that provide incentives to generators to supply reactive power while preventing the abuse of market power. This paper proposes a mathematical model to simulate the strategic behavior of generators supplying reactive power while considering the system operator's schedule. The proposed method can be used by the regulator to simulate the market behavior in the reactive power supply. We further study how regulatory policies affect the strategic behavior. An alternative price cap method has been proposed and tested in the numerical example to mitigate the effect of strategic behavior of generators in reactive power procurement by the system operator. The numerical examples are tested on the Nordic 32-bus system. [ABSTRACT FROM AUTHOR]

This paper proposes a two-level framework for the operation of a competitive market for reactive power ancillary services. It is argued that the first-level, i.e., reactive power procurement, be on a seasonal basis while the second-level, i.e., reactive power dispatch, be close to real-time operation. To this effect, a reactive power procurement market model is proposed here taking into consideration system security aspects. This procurement procedure is based on a two-step optimization model. First, the marginal benefits of reactive power supply from each provider with respect to system security are obtained by solving an optimal power flow (OPF) that maximizes system loadability subject to transmission security constraints imposed by voltage limits, thermal limits, and stability limits. Second, the selected set of generators is then determined by solving an OPF-based auction to maximize a societal advantage function comprising generators' offers and their corresponding marginal benefits with respect to system security, considering all transmission system constraints. The proposed procedure yields the selected set of generators and zonal price components, which would form the basis for seasonal contracts between the system operator and the selected reactive power service providers. [ABSTRACT FROM AUTHOR]

In this paper, we present the design ofa localized competitive market for reactive power ancillary services at the level of individual voltage-control areas. The concept of electrical distance has been used to identify the different voltage-control areas within a power system. The proposed reactive power market is settled on uniform price auction, using a modified optimal power-flow model. Uniform prices for various components of reactive power service are obtained for each voltage-control area. In the study cases described in the paper, we examine whether such a localized reactive power market is more desirable than a common system-wide reactive power market. [ABSTRACT FROM AUTHOR]

Analyzes the design of a competitive market for reactive power ancillary services. Uses of generator-reactive power-capability characteristics; Components of payment for reactive power; Factors that affected the operations of reactive power services.

Presents information on a study which examined the problem of reactive power procurement by an independent system operator in deregulated electricity markets. Methodology of the study; Results and discussions.

Presents a reply to comments on a study on reactive power management. Use of independent transmission companies in the procurement of reactive power services; Capabilities of capacitor banks; Variations in the way reactive power is managed.

This paper presents the design of a competitive market for reactive power ancillary services. Generator reactive power capability characteristics are used to analyze the reactive power costs and subsequently to construct a bidding framework. The reactive power market is settled on uniform price auction, using a compromise programming approach based on a modified optimal power flow model. The paper examines market power issues in these markets and identifies locations where strategic market power advantages are present that need to be removed through investments in reactive power devices. [ABSTRACT FROM PUBLISHER]