•Due to energy preservation and precharge abilities, a BSU (Battery Storage Unit) should forecast market outcomes for two days in advance in order to maximize its overall profits.•BSU will behave in ...a way to minimize its impact on LMPs. For this reason, it may discharge/charge at hours whose LMPs are not highest/lowest.•Coordinated BSU strategy in the day-ahead market results in significantly higher profits as compared to the uncoordinated approach.•In the uncoordinated approach, BSU profits are highly dependent on the BSU scheduling sequence, which means that there are many equilibria with uneven distribution of profits.
Energy storage is gaining an important role in modern power systems with high share of renewable energy sources. Specifically, large-scale battery storage units (BSUs) are an attractive solution due to their modularity, fast response and ongoing cost reduction.
This paper aims to formulate, analyze and clarify the role of merchant-owned BSUs in the day-ahead electricity market. It defines virtual storage plant (VSP) as a set of BSUs distributed across the network. A VSP offering model is formulated as a bilevel program in which the upper-level problem represents the VSP profit maximization and operation, while the lower-level problem simulates market clearing and price formation. This mathematical problem with equilibrium constraints (MPEC) is converted into a mixed-integer linear program (MILP). This is afterwards expanded to a game of multiple VSPs formulating an equilibrium problem with equilibrium constraints (EPEC), which is solved using the diagonalization procedure.
The proposed model is applied to an updated IEEE RTS-96 system. We evaluate the impact VSPs have on the locational marginal prices and compare the coordinated approach (all BSUs operated under a single VSP), i.e. the MPEC formulation, to the competitive approach (multiple VSPs competing for profit), i.e. the EPEC formulation.
The paper presents accurate and simple dynamic model of a supercapacitor bank system for power system dynamics studies. The proposed model is derived from a detailed RC circuit representation. ...Furthermore, a complete control system of the supercapacitor bank is also presented. The proposed model is easy to integrate in any power system simulation software and consists of only up to four standard datasheet parameters. The performance of the proposed model in grid frequency control and low-voltage ride through is illustrated on IEEE 14-bus test system in DIgSILENT PowerFactory. It is shown that in case of transient stability simulations the ideal (simplified) model of the supercapacitor can be used while in case of frequency control the ideal representation may not always be appropriate.
Unatoč razvoju tržišta električne energije izračun troškova proizvodnje/potrošnje jalove snage sinkronih generatora te mrežnih kompenzacijskih uređaja još uvijek nije u potpunosti definiran, a ...uspostava tržišnih mehanizama za jalovu snagu u većini je zemalja još uvijek u začetku. Razlog tomu je mali ekonomski značaj optimiranja tokova jalove snage. Zbog svojeg utjecaja na mogućnost prijenosa djelatne snage, te povezanosti s iznosima napona u sustavu, a time i s naponskom stabilnošću elektroenergetskog sustava, jalova snaga zaslužuje pažnju i ozbiljna razmatranja s ciljem definiranja metodologije za određivanje njene cijene na tržištu. U članku je
opisana problematika određivanja troškova proizvodnje/potrošnje jalove snage te su navedeni mehanizmi za uspostavu tržišta jalovom snagom. Dan je pregled značajnijih modela tržišta jalovom snagom uspostavljenih u svijetu.
•Impact of increased wind generation on a power system frequency transient response.•Impact of wind capacity, electrical distance and grid configuration on initial RoCoF.•The power system model ...developed with highly detailed components in Matlab/Simulink.•Real-life data were used for model parameterization and scenario analysis.
Increased wind energy penetration influences the power system dynamic response to transient disturbances. Replacement of conventional production units with converter-connected wind turbines reduces natural power system inertia contained in rotational masses of synchronously connected turbine-generator units, therefore creating low-inertia power systems. Such a transition has an adverse effect on system resilience to disturbances and on the capability to maintain stable operation. This research examines the impact of high regional wind power production on system transient stability in the case of island operation of the Croatian power system. The system is divided into four geographical areas modeled as four centers of inertia with aggregated parameters. The study investigated initial transient RoCoF values in different areas for current and future wind capacity share scenarios, loading data, and primary frequency regulation settings. The modeling and scenario analysis have been performed on a detailed phasor power system model in the MATLAB/Simulink environment.
Distributed transmission-scale energy storage is becoming economically feasible due to the growing share of renewable generation and cost reduction of specific storage technologies, primarily ...batteries. Under these circumstances, independent merchants may start investing in storage facilities. On the other hand, system operators, besides investing in transmission lines, may, under certain conditions, invest in storage units as well. This paper formulates a trilevel model where the upper-level problem optimizes the system operator's transmission line and energy storage investments, the middle-level problem determines merchant energy storage investment decisions, while the lower level problem simulates market clearing process for representative days. After replacing the lower level problem with its primal dual equivalent conditions, the middle- and lower level problems are merged into a mixed-integer problem with equilibrium constraints. The resulting bilevel structure is iteratively solved using a cutting plane algorithm. The proposed formulation is first applied to a six-bus system to present the mechanics of the model and then to the IEEE RTS-96 test system. The results show that even at the low cost of energy storage, the system operator (SO) still prefers line investments, while merchant investments are driven by the volatility of LMPs. Both the SO and merchant investments increase the social welfare, although this increase is mostly driven by the SO investments.
This Special Issue presents extended versions of selected top papers of the Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion (MEDPOWER), held in ...Dubrovnik in 2018. The 11th Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion (MEDPOWER 2018) was held in Cavtat, Dubrobnik, Croatia, from 12 to 15 November 2018. The conference gathered more than 200 scientists, researchers, and experts from all around the world. A total of 147 oral presentations were held during the conference, with an additional 50 papers presented in special sessions. The top 10 papers have been selected for this Special Issue in Energies, covering a variety of topics from end-user challenges, distribution and transmission network operation and planning, to generation planning and modeling.
•Cavitation phenomena causes oscillations in bulb turbines with low tailwater level.•Oscillations can be tied to a disturbance on a single runner blade.•Turbine model based on draft tube pressure for ...simulation of oscillations.•Proposed model is validated using real hydro power plant data and measurements.
Generic dynamic models of hydraulic turbines are unable to capture power oscillations phenomena originating from a torque disturbance on a single runner blade. In this paper, an improved dynamic model of a double-regulated hydraulic turbine which takes into account torque oscillations identified from draft tube pressure measurements was presented. It was experimentally identified that specific power oscillations of a bulb turbine operating with low tailwater level can be connected to cavitation-related phenomena on a single runner blade. Furthermore, it was shown that these oscillations do not originate from grid fault-induced resonance between the turbine rotor and generator, nor from the excitation system. The proposed simulation model was validated against measurement data of hydro power plant Dubrava and the validation shows good agreement between measured and simulated results.
•Turbine governor inclusion with adaptive thresholds for avoiding UFLS stages activation.•Design of UFLS scheme based on prediction of fnadir considering multiple activation stages.•Independence from ...ROCOF measurements and application to multi-machine models.
The increased integration of the new generation technologies into the electric power system (EPS) which are mainly inverter-based changes its characteristics. The main issue that arises is the appearance of faster frequency dynamics that are caused by production connected through inverters. This leads to the need for changing conventional under-frequency load shedding (UFLS) schemes because, in cases of high dynamics of frequency change, conventional UFLS algorithms are not able to stop initial frequency drop and prevent power system collapse. This paper proposes reconfiguration method for conventional strategies transforming their response from static and inflexible to a dynamic and adaptive one. The focus of the paper is the proposed method for dynamical change of UFLS stage thresholds to minimize the number of activated UFLS stages during a particular disturbance event and therefore enable more efficient response of the system to further disturbances. The method effectiveness was demonstrated on a multi-machine power system model consisting of various generation technologies.
•Configuration planning of MES in Beijing subsidiary administrative center is drawn.•An MILP based two-stage model is used to obtain the optimal planning scheme.•Sensitivity analysis shows how load ...profiles and energy prices impact the planning.•Operation simulation is performed on optimal planning scheme and four alternatives.
Multi-energy systems (MES) contribute to increasing energy utilization efficiency and renewable energy accommodation by coupling multiple energy sectors. Beijing is planning to build a subsidiary administrative center in Tongzhou District. A new MES will be built in this center from scratch to jointly meet electricity, heat and cooling demands. This raises the need for optimizing the configuration of MES from scratch at the planning stage. In this paper, the configuration planning of the MES in Beijing’s new subsidiary administrative center is conducted using a two-stage mixed-integer linear programming (MILP) approach based on the energy hub (EH) model. Given the load demand, distributed renewable energy sources, energy prices and candidate system component parameters, the MES configuration planning, equipment selection and capacity planning are jointly managed without limiting the possibility of MES configuration. A sensitivity analysis is performed to show the impacts of load profiles and energy prices on the optimal MES configuration. Operation simulations are carried out based on the obtained optimal planning scheme and another four alternative planning schemes presented by Beijing subsidiary administrative center. The operating cost, CO2 emission and overall system efficiency of each planning scheme are calculated and compared with each other.
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