► A two-stage stochastic offering model for a virtual power plant is presented. ► The virtual power plant consists of an intermittent source, a dispatchable source and a storage unit. ► The virtual ...power plant trades in the day-ahead and balancing markets. ► Characteristic scenarios are thoroughly analyzed and relevant conclusions are drawn.
A virtual power plant aggregates various local production/consumption units that act in the market as a single entity. This paper considers a virtual power plant consisting of an intermittent source, a storage facility, and a dispatchable power plant. The virtual power plant sells and purchases electricity in both the day-ahead and the balancing markets seeking to maximize its expected profit. Such model is mathematically rigorous, yet computationally efficient.
The offering problem is cast as a two-stage stochastic mixed-integer linear programming model which maximizes the virtual power plant expected profit. The uncertain parameters, including the power output of the intermittent source and the market prices, are modeled via scenarios based upon historical data. The proposed model is applied to a realistic case study and conclusions are drawn.
Increasing variability and uncertainty coming from both sides of the power system equilibrium equation, such as wind energy on the generation side and increasing share of new consumers such as ...electric vehicles on the demand side, entail higher reserve requirements. While traditional approaches of assigning conventional generation units to maintain system stability can increase operational costs, greenhouse gas emissions, or give signals for new investments, utilizing intelligent control of distributed sources might mitigate those negative effects. This can be achieved by controllable charging of domestic electric vehicles. On the other hand, increasing number of public charging stations gives final users the opportunity to fast charge, making their vehicles an additional source of uncertainty rather than a provider of flexibility. This paper brings a full system assessment of combined effect of slow home charging of electric vehicles together with fast charging stations (both with and without integrated energy storage systems), cast as mixed integer linear programming unit commitment model. The contributions of this paper look into optimal periods when fast charging is beneficial for the system operation, as well as assess the benefits of integrating battery storage into fast charging stations to mitigate the negative effects to power system operation.
•Multi-area models are more accurate in studying power frequency dynamics.•Distant generating units sense the frequency change with a certain time delay.•Allowing generators to start adjusting their ...power earlier.•Proposed research aims to improve stability using PMUs in real-time.
In the interconnected power systems, the frequency change during disturbances may manifest differently in certain areas in the initial moments after the disturbance. Due to wave propagation, generating units located in distant areas contribute to primary frequency control (PFC) with a certain time delay. To address this issue, this study presents a novel primary frequency control (PFC) mechanism that enables generators in remote areas to adjust their output power before the disturbance wave propagates to that area. This mechanism leverages the use of PMU systems to enable early power adjustments. The proposed PFC mechanism is applicable to both conventional interconnected power systems and future systems with a significant share of converter-based technologies. The effectiveness of the method is demonstrated through simulations conducted on a two-area power system model, showing a 15 % reduction in maximum frequency deviation compared to the conventional method. This improvement results in a lower frequency nadir, offering the potential for a decrease of frequency nadir of up to 0.2 Hz when the disturbance causes the frequency drop to 49 Hz.
This paper presents a nonlinear dynamic simulation model of an ultracapacitor (UC) bank and the associated control system. The control system at hand consists of two levels: the lower level controls ...the inverter of the UC bank, while the upper control level is responsible for providing charging/discharging active power set points to be followed by the lower control level. This paper focuses on the development of the upper control level for frequency control. Specifically, two simulation case studies are developed so as to assess the performance of the proposed control framework. In the first case study the upper control level is developed using a classical Proportional-Integral-Derivative (PID) controller. In the second case study the upper control level is devised using a Model Predictive Control (MPC) algorithm based on internal linear prediction model of a nonlinear UC bank. In both cases, a nonlinear UC bank simulation model is used. The simulation case studies are modelled and tested in Matlab/Simulink. The response of the MPC-controlled UC bank is compared to the 3 existing PID-control algorithms for frequency control. The simulation results show that the MPC algorithm outperforms the conventional PID controllers.
In a power system with a high-share of photovoltaic systems, the frequency response can be improved by the participation of photovoltaics in frequency control. If the photovoltaic system operates at ...reduced power, in a so-called de-loaded mode, and maintains a specific amount of power reserve, then participation in system frequency control is usually realized by a droop control method. The implementation of this method is very simple, but it does not provide the recovery of PV power reserve before the secondary frequency control reacts. This means the PV system cannot provide additional support to the grid if a new disturbance occurs in a short time following the first one. This paper presents a novel approach for PV system control in providing support to system frequency. The novel control algorithm aims to enable rapid recovery of PV power reserve which makes the PV system capable of providing support to the cascading disturbance events. The development of such PV system control model is based on a detailed mathematical analysis of the dynamic frequency response. The effectiveness of the proposed method was tested on a two-area multi-machine power system model and through 4 different study cases.
In the recent years, frequency support from converter-connected wind power generation has been a hot topic in the field of power system dynamics and control. At the same time, the share of wind ...generation in the power systems worldwide has significantly risen. Therefore, it is necessary to discuss a new approach to low-order system frequency response (SFR) modelling of power systems. In this paper, a new low-order SFR model of a power system with high penetration of wind power generation is proposed by taking into account the different operating regimes of variable-speed wind turbine generators (VSWTGs). The results are compared to the nonlinear transient stability dynamic models to show that the low-order model adequately describes the nonlinear model. The proposed model can be used (e.g. by researchers, students or power system operators) to qualitatively simulate power system frequency behaviour for different operating scenarios.
Local energy sharing (LES) is a concept that enables sharing between distribution system participants such as consumers, producers, and prosumers at the local level in a transparent and cooperative ...manner. It can improve local supply-demand balancing, reduce voltage deviations, and improve social welfare. However, the feasibility of such an approach is highly dependent on the regulatory framework and implementation requires investment in an adequate information and communication infrastructure. This paper examines components for the implementation of LES within energy communities in the EU, with a focus on price-forming methods that can be integrated into a net-billing system and adopted for different regulatory set-ups. Further, a method for the assessment of impacts on market participants is provided. The approach is applied for the assessment of the opportunities for LES in the city of Križevci, considering local generation, flexibility options, and real-life regulatory requirements. It is shown that LES under appropriate regulatory provisions can be an effective market-based mechanism for stimulating local generation and flexibility activation, and that way support decarbonization and local self-sufficiency. All members can benefit from participating in the energy community, but the distribution of the benefits notably depends on the applied LES price-forming method. On the other hand, subject to regulatory setup, the trade-offs are reflected on reduced revenues for market participants that generate income based on transmission fees, taxes, and/or surcharges.
•Components for local energy sharing (LES) implementation within energy communities.•Framework for feasibility evaluation of LES under different regulatory set-ups.•MILP LES market-clearing model with energy sharing compensation price method.•LES price-forming methods integrated into a net-billing system.•Simulation of LES as a market with a local energy sharing coordinator.
•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.
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.
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.
PDF
