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In this paper, the mathematical model of an electricity generator with four static magnets and four dynamic magnets is suggested for the electricity generation. The introduced electricity generator is based on the electricity generator with two static magnets and two dynamic magnets, but it has three main advantages: it has more interactions between the static and dynamic magnets, it generates more electricity, and it generates smoother signals. Electricity generators are compared for the electricity generation. [ABSTRACT FROM AUTHOR]

This paper discusses the conceptual design and operation of an isolated power system, recognizing the reality that generator or turbine trips will occur. The level of reserve generating capacity must be set with proper balancing of capital expenditures and operating costs against revenue lost in a production shutdown. The way that reserve capacity is provided is as important as the amount of reserve; seemingly adequate reserve can turn out to be badly insufficient if it is not well distributed across the available reserve sources. The dynamic behavior of reserve capacity, as much as the amount of capacity that is ultimately available, is critical in determining how an isolated facility will behave in the wake of a unit trip or the loss of a grid connection. In this paper, experiences with detailed dynamic simulations of a range of isolated systems are described. These are related to test work and operational incidents that have provided practical calibrations. Based on simulation and experience, some guidelines are offered for configuring generation and selecting strategies for maintaining stability in large, isolated continuous-process facilities. [ABSTRACT FROM PUBLISHER]

Part one of this two-part paper presents new models for evaluating flexible resources in two-settlement electricity markets (day-ahead and real-time) with uncertain net loads (demand minus wind). Physical resources include wind together with fast- and slow-start demand response and thermal generators. We also model financial participants (virtual bidders). Wind is stochastic, represented by a set of scenarios. The two-settlement system is modeled as a two-stage process in which the first stage involves unit commitment and tentative scheduling, while the second stage adjusts flexible resources to resolve imbalances. The value of various flexible resources is evaluated through four two-settlement models: 1) an equilibrium model in which each player independently schedules its generation or purchases to maximize expected profit; 2) a benchmark (expected system cost minimization); 3) a sequential equilibrium model in which the independent system operator first optimizes against a deterministic wind power forecast; and 4) an extended sequential equilibrium model with self-scheduling by profit-maximizing slow-start generators. A tight convexified unit commitment allows for demonstration of certain equivalencies of the four models. We show how virtual bidding enhances market performance, since, together with self-scheduling by slow-start generators, it can help a deterministic day-ahead market to choose the most efficient unit commitment. [ABSTRACT FROM PUBLISHER]

This paper proposes a new mathematical structure for evaluating the economic efficiency of transmission investment in a liberalized electricity market. The problem faced by a transmission planner is modeled using the concept of social welfare from economics. The behavior of generators is modeled as the Nash equilibrium of a strategic game. The Nash solution concept is reformulated as an optimization problem and a new concept—the Stackelberg-Worst Nash equilibrium—is introduced to resolve the problem of multiple equilibria. The proposed structure can take into account the effects of a transmission augmentation on both market power and strategic generation investment. Accordingly, the optimal solution to the transmission planner's problem may allow additional transmission capacity both to reduce market power and to defer investment in the generation sector. A methodology is proposed to decompose the benefits of a transmission augmentation policy into the efficiency benefit, competition benefit, and the deferral benefit. The outcomes of the proposed approach to transmission augmentation are compared with the outcomes of two other approaches to transmission augmentation using a simple three-bus network example. [ABSTRACT FROM PUBLISHER]

In traditional power system, economic dispatch and generation control are separately applied. Online generation adjustment is necessary to regulate generation reference for real-time control to realize economic operation of power systems. Since most economic dispatch solutions are centralized, they are usually expensive to implement, susceptible to single-point-failures, and inflexible. To address the above-mentioned problems, this paper proposed a multi-agent system based distributed control solution that can realize optimal generation control. The solution is designed based upon an improved distributed gradient algorithm, which can address both equality and inequality constraints. To improve the reliability of multi-agent system, the N-1 rule is introduced to design the communication network topology. Compared with centralized solutions, the distributed control solution not only can achieve comparable solutions but also can respond timely when the system experiences change of operating conditions. MAS based real-time simulation results demonstrate the effectiveness of the proposed solution. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a distributed recharging rate control algorithm which combines the objectives of regulating frequency and improving the utilization of electric generators. An incentive policy \kappa is created that encourages electric vehicles (EVs) to demand energy when non-EV demand is low and electric generators are underutilized. EVs also act as frequency regulators which can control their participation role by modifying their respective payment rate wi. The proposed distributed recharging rate control algorithm can realize a Demand Management solution for EVs and does not require explicit real time communication from the electric generators or between the recharging sockets. A mechanism is presented that can trade off an ideal incentive policy with its approximation and enable the integration of the proposed controller with legacy protection system. Simulation is used to assess the algorithm and to highlight its embedded characteristics. [ABSTRACT FROM PUBLISHER]

Paper presents an equivalent model of an active distribution network cell (ADNC) with distributed generation for transmission system stability studies. The equivalent model of ADNC comprises a converter-connected generator and a composite load model in parallel. The gray-box approach was chosen as it enables inclusion of prior knowledge about the ADNC structure into the model development, hence making the model more physically relevant and intuitive than a black-box or white-box model. The dynamic equivalent model is presented in a seventh-order nonlinear quasi state space format, developed from the algebraic and differential equations describing assumed typical components of the ADNC. The developed equivalent model of ADNC was validated through small and large disturbance studies using the modified IEEE nine-bus transmission system model. [ABSTRACT FROM PUBLISHER]

In this paper, an oscillating water column-based wave energy conversion plant is modeled and controlled by means of two complementary control strategies in order to improve the conversion of wave energy into electric power. This wave power generation system consists of a capture chamber, a Wells turbine, and an induction generator. The improvement relays on the implementation of a control scheme that combines two different control methods: a rotational speed control and an airflow control implemented by means of a throttle valve in series with the turbine. The use of rotational speed control provides a fast way to react to the abrupt and short changes in the turbine speed, ensuring that the average power of the generator is adequately adjusted according to the incident wave power level. Besides, a throttle-valve is used to control the flow through the turbine so as to increase the amount of energy produced, particularly at the higher incident wave power levels. These two control strategies complement each other, maximizing and improving the quality of supply by controlling and smoothing the generated power for different scenarios of wave oscillations, variations of wave grouping, and changes in the sea state. [ABSTRACT FROM AUTHOR]

This paper proposes an active-reactive power dispatch procedure that is expressed via a bilevel optimization problem whose upper and lower level criteria are, respectively, the minimum opportunity cost and minimum offered price of active power. It analyzes the impact of minimizing such criteria on system operation, and it investigates the behavior of marginal prices and opportunity costs and their use in mechanisms to compensate generators for power provision. The bilevel problem is solved using a version of interior point methods derived for mathematical programs with complementarity constraints. Results obtained with three test systems are analyzed. [ABSTRACT FROM PUBLISHER]

In response to the challenges brought by uncertain bus load and volatile wind power to power system security, this paper presents a novel unit commitment formulation based on interval number optimization to improve the security as well as economy of power system operation. By using full-scenario analysis, the worst-case impact of volatile node injection on unit commitment is acquired, so that the proposed model can always provide a secure and economical unit commitment result to the operators. Scenarios generation and reduction method based on interval linear programming theory are used to accelerate the solution procedure without loss of optimality. Benders decomposition is also implemented to reduce the complexity of this large-scale interval mixed integer linear programming, and prove the rationality and rigor of our proposed method. The numerical results indicate better secure and economical features of the proposed method comparing with the traditional one. [ABSTRACT FROM PUBLISHER]

This paper presents a new field test to adequately assess the oscillation damping effectiveness of the PSSs in a multigenerator power plant. The test allows estimating the location of the dominant open-loop poles (i.e., in the absence of PSSs at the multigenerator plant) from frequency response measurements of the closed-loop multivariable system. This test was first carried out at the Itaipu 60-Hz power station, which was generating 4000 MW at the time. The test validation was made through comparison of obtained frequency response measurements with computer simulations of a detailed dynamic model of the Brazilian interconnected power system. [ABSTRACT FROM AUTHOR]

This paper presents a new approach for the contingency-constrained single-bus unit commitment problem. The proposed model explicitly incorporates an n - K security criterion by which power balance is guaranteed under any contingency state comprising the simultaneous loss of up to K generation units. Instead of considering all possible contingency states, which would render the problem intractable, a novel method based on robust optimization is proposed. Using the notion of umbrella contingency, the robust counterpart of the original problem is formulated. The resulting model is a particular instance of bilevel programming which is solved by its transformation to an equivalent single-level mixed-integer programming problem. Unlike previously reported contingency-dependent approaches, the robust model does not depend on the size of the set of credible contingencies, thus providing a computationally efficient framework. Simulation results back up these conclusions. [ABSTRACT FROM PUBLISHER]

Incentives to encourage the uptake of renewable energy generation have fostered wind energy in many power systems. These incentives usually take the form of market instruments (e.g., feed-in tariff or premium) that are not directly amenable to optimization representations of the market. In this paper, we propose an equilibrium model of the short-term market to address the impact of wind operation under different structural assumptions. The model is formulated for several price taking, risk averse firms in competition. It accounts for wind generation uncertainty and embeds a representation of the day ahead and balancing mechanisms. The consumer is modeled by a linear inverse demand function. We focus on feed-in premium as the incentive to wind as this is the instrument most favored today in European discussions. The model is formulated as a stochastic equilibrium problem where the Karush-Kuhn-Tucker (KKT) conditions from the optimization problem of each firm are simultaneously solved together with market clearing conditions on energy, capacity for reserve and energy for reserve. The problem for each firm consists of a two-stage stochastic optimization problem with a recourse function based on the conditional value at risk (CVaR\theta ) as a risk measure. Due to price taking assumptions the model is a single stage complementarity problem; it is implemented and solved using the software GAMS. An example based on a stylized simplification of the Spanish power market and motivated by the impact of wind penetration on the revenue of conventional plants is used to illustrate the proposed approach. [ABSTRACT FROM PUBLISHER]

With high wind-power penetration, power-system operators require accurate wind-power output from wind farms for system operation. A more accurate four-dimension wind speed model is proposed in this paper to simulate the effects of terrain and time delay of wind speed. Two coordinate transformation matrices are proposed to easily incorporate wind direction in wind-speed simulation. The effects of random failures and wake of wind turbine generators on wind-speed distribution in a wind farm are also considered in the proposed model. A sequential Monte Carlo simulation technique is developed to evaluate adequacy of power systems with wind farms using the proposed model. The modified IEEE RTS is analyzed to illustrate the models and technique. The simulation results show that those factors have significant impact on power output of a wind farm and system reliability. [ABSTRACT FROM PUBLISHER]

Load demand in small autonomous island systems is typically covered by Diesel Units (DU). Although a favourable renewable energy source (RES) potential might exist, the technical constraints introduced by the conventional generators result in relatively low RES penetration levels, typically up to 15%–20% of the annual energy demand. To overcome such limitations, introduction of energy storage is necessary. In the case of very small islands (less than 1 MW peak load), lead-acid battery energy storage systems (BESS) constitute a technically mature solution with considerable application potential. In this paper, the potential for achieving very high RES penetration levels with the introduction of BESS in an existing small island system is investigated. An operating policy is first introduced for the overall system, including conventional generators, RES (wind and photovoltaic) stations and storage system. Simulation results are then presented to quantify the expected energy benefits in terms of RES energy penetration and the impact on the economics of the island system. The sizing of the hybrid system components is then investigated by conducting a parametric analysis and then optimized by applying genetic algorithms. [ABSTRACT FROM PUBLISHER]

This paper presents a model-based optimization approach to determine operation mode of a set of fans in the cooling tower (CT) by considering turbine generator and CT as an integrated system. The optimization problem is formulated as to maximize the net power output, which is the result of subtracting power consumption of fans in CT from power generated by turbine generator. The operations of both units are characterized by a data-driven method, local model network, which presents a set of local models in the formats of linear equations. Stepwise variable selection is employed to identify key variables as a way of reducing the number of variables and avoiding overfitting. Satisfactory fuzzy c-mean cluster is used to categorize operation data into several groups to build local models. The optimal problem is then solved by linear programming algorithm. A case study conducted in a commercial plant demonstrates that the proposed approach can increase significant net power output. [ABSTRACT FROM PUBLISHER]

In this study, two important planning problems in power systems that are transmission expansion and reactive power are formulated as a mixed-integer linear programming taking into account the bilevel structure due to the consideration of market clearing under several load-wind scenarios. The objective of the proposed method is to minimize the installation cost of transmission lines, reactive power sources, and the annual operation costs of conventional generators corresponding to the curtailed wind energy while maintaining the reliable system operation. Lower level problems of the bilevel structure are designated for the market clearing which is formulated by using the linearized optimal power flow equations. In order to obtain mixed-integer linear programming formulation, the so-called lower level problems are represented by using primal-dual formulation. By using the proposed method, power system planners will be able to find economical investment plans by considering the balance between wind power curtailment and the installation of transmission lines and reactive power sources. [ABSTRACT FROM AUTHOR]

The authors present their insights into an article by L. Ding, F. M. Gonzalez-Longatt, P. Wall and V. Terzija about the use of a fast controlled algorithm to split a large-scale power system based on a two-step spectral clustering. They seek clarification on the article's discussion on the spectral clustering controlled islanding (SCCI) algorithms and the determinant of the number of coherent generator groups in the IEEE 39-bus test system.

The ever-increasing penetration of variable wind energy in power systems affects the hourly dispatch of thermal power generation in electricity markets. The variability of wind energy, which makes the wind energy non-dispatchable and difficult to control, could bring significant challenges to power system operators. The hourly coordination of wind power generation units with pumped-storage hydro (PS) generation could relieve the variability of wind energy and increase its dispatchability. The wind-PS coordination is based on the application of stochastic security-constrained unit commitment (stochastic SCUC). In this study, the coordinated hourly bus-level scheduling of wind-PS is compared with the coordinated system-level operation strategies in the day-ahead scheduling of power systems. [ABSTRACT FROM PUBLISHER]

We present a two-stage stochastic programming model for committing reserves in systems with large amounts of wind power. We describe wind power generation in terms of a representative set of appropriately weighted scenarios, and we present a dual decomposition algorithm for solving the resulting stochastic program. We test our scenario generation methodology on a model of California consisting of 122 generators, and we show that the stochastic programming unit commitment policy outperforms common reserve rules. [ABSTRACT FROM PUBLISHER]

Constraints in fuel supply, electricity generation, and transmission interact to affect the welfare of strategic generators and price-sensitive consumers. We consider a mixed integer bilevel programming model in which the leader makes capacity expansion decisions in the fuel transportation, generation, and transmission infrastructure of the electricity supply network to maximize social welfare less investment cost. Based on the leader's expansion decisions, the multiple followers including the fuel suppliers, ISO, and generation companies simultaneously optimize their respective objectives of cost, social welfare, and profit. The bilevel program is formulated as a mathematical program with complementarity constraints. The computational challenge posed by the discrete character of transmission expansions has been managed by multiple model reformulations. A lower bound provided by a nonlinear programming reformulation increases the efficiency of solving a binary variable reformulation to global optimality. A single-level optimization relaxation serves as a competitive benchmark to assess the effect of generator strategic operational behavior on the optimal capacity configuration. [ABSTRACT FROM PUBLISHER]