| 1. |
- Abolpour, Roozbeh, et al.
(författare)
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A New Power Flow Model With a Single Nonconvex Quadratic Constraint : The LMI Approach
- 2022
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Ingår i: IEEE Transactions on Power Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8950 .- 1558-0679. ; 37:2, s. 1218-1229
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a new mathematical model for power flow problem based on the linear and nonlinear matrix inequality theory. We start with rectangular model of power flow (PF) problem and then reformulate it as a Bilinear Matrix Inequality (BMI) model. A Theorem is proved which is able to convert this BMI model to a Linear Matrix Inequality (LMI) model along with One Nonconvex Quadratic Constraint (ONQC). Our proposed LMI-ONQC model for PF problem has only one single nonconvex quadratic constraint irrespective of the network size, while in the rectangular and BMI models the number of nonconvex constraints grows as the network size grows. This interesting property leads to reduced complexity level in our LMI-ONQC model which in turn makes it easier to solve for finding a PF solution. The non-conservativeness, iterative LMI solvability, well-defined and easy-to-understand geometry and pathwise connectivity of feasibility region are other important properties of proposed LMI-ONQC model which are discussed in this paper. An illustrative two-bus example is carefully studied to show different properties of our LMI-ONQC model. We have also tested our LMI-ONQC model on 30 different power-system cases including four ill-conditioned systems and compared it with a group of existing approaches. The numerical results show the promising performance of our LMI-ONQC model and its solution algorithm to find a PF solution.
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| 2. |
- Alvehag, Karin, et al.
(författare)
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Impact of Reward and Penalty Scheme on the Incentives for Distribution System Reliability
- 2014
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Ingår i: IEEE Transactions on Power Systems. - 0885-8950 .- 1558-0679. ; 29:1, s. 386-394
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Tidskriftsartikel (refereegranskat)abstract
- Performance-based regulations accompanied by quality regulations are gaining ground in the electricity distribution business. Several European countries apply quality regulations with reward and penalty schemes (RPSs), where the distribution system operator (DSO) is rewarded (or penalized) when fulfilling (or not fulfilling) an adequate level of reliability to its customers. This paper develops a method that the regulator can use before enforcing a regulation to get an understanding of the impact different RPS design solutions have on the DSO's financial risk and incentives to invest in reliability. The proposed method also includes a sensitivity analysis to identify which are the most important parameters in an RPS. The new method is applied to three regulatory challenges to evaluate their RPS design solutions. Results show that the choice of scheme design and cost model used to decide the incentive rate have a large impact on the DSO's financial risk and incentive to invest.
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| 3. |
- Amelin, Mikael
(författare)
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An Evaluation of Intraday Trading and Demand Response for a Predominantly Hydro-Wind System Under Nordic Market Rules
- 2015
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Ingår i: IEEE Transactions on Power Systems. - 0885-8950 .- 1558-0679. ; 30:1, s. 3-12
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Tidskriftsartikel (refereegranskat)abstract
- Many countries are planning for a large-scale expansion of wind power. This development will have a significant impact on power system operation and economics. One of the challenges is that the difficulty to forecast wind power generation will increase the need for real-time balancing. This paper presents a study of how the impact of wind power forecast errors can be reduced by changes in the market design. The study is based on the conditions in the Nordic electricity market. A characteristic of this market is that there is a large share of flexible hydro generation; hence, ramp and unit commitment constraints rarely constrain dispatch. The need for regulation during real-time is provided in a voluntary real-time balancing market, where players can be compensated for their redispatch costs. Case studies are presented which show that a shift from day-ahead to intraday trading and increased demand response can improve the performance when the share of wind power is increasing.
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| 4. |
- Amelin, Mikael
(författare)
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Comparison of Capacity Credit Calculation Methods for Conventional Power Plants and Wind Power
- 2009
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Ingår i: IEEE Transactions on Power Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8950 .- 1558-0679. ; 24:2, s. 685-691
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Tidskriftsartikel (refereegranskat)abstract
- Several methods for computing capacity credit values of power plants have been presented over the years. This paper uses an empirical approach to investigate and compare different properties of four typical capacity credit definitions. It is shown that the choice of definition indeed can have a significant impact on the results. Concerning three of the analyzed methods, it is found that important factors that influence the capacity credit are the overall generation adequacy and the penetration factor of the power plant; this means that the same generating unit will generally have a higher capacity credit if added to a system with high loss of load probability, and the unit will have a higher capacity credit if its installed capacity is small compared to the total installed capacity of the system. The results of the fourth method only depend on the size and availability of the generating units.
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| 5. |
- Andersen, Martin S., et al.
(författare)
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Reduced-Complexity Semidefinite Relaxations of Optimal Power Flow Problems
- 2014
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Ingår i: IEEE Transactions on Power Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8950 .- 1558-0679. ; 29:4, s. 1855-1863
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Tidskriftsartikel (refereegranskat)abstract
- We propose a new method for generating semidefinite relaxations of optimal power flow problems. The method is based on chordal conversion techniques: by dropping some equality constraints in the conversion, we obtain semidefinite relaxations that are computationally cheaper, but potentially weaker, than the standard semidefinite relaxation. Our numerical results show that the new relaxations often produce the same results as the standard semidefinite relaxation, but at a lower computational cost.
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| 6. |
- Andreasson, Martin, et al.
(författare)
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Distributed Frequency Control Through MTDC Transmission Systems
- 2017
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Ingår i: IEEE Transactions on Power Systems. - : IEEE Press. - 0885-8950 .- 1558-0679. ; 32:1, s. 250-260
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose distributed dynamic controllers for sharing both frequency containment and restoration reserves of asynchronous ac systems connected through a multi-terminal HVDC (MTDC) grid. The communication structure of the controller is distributed in the sense that only local and neighboring state information is needed, rather than the complete state. We derive sufficient stability conditions, which guarantee that the ac frequencies converge to the nominal frequency. Simultaneously, a global quadratic power generation cost function is minimized. The proposed controller also regulates the voltages of the MTDC grid, asymptotically minimizing a quadratic cost function of the deviations from the nominal dc voltages. The results are valid for distributed cable models of the HVDC grid (e.g., $\pi$-links), as well as ac systems of arbitrary number of synchronous machines, each modeled by the swing equation. We also propose a decentralized communication-free version of the controller. The proposed controllers are tested on a high-order dynamic model of a power system consisting of asynchronous ac grids, modeled as IEEE 14 bus networks, connected through a six-terminal HVDC grid. The performance of the controller is successfully evaluated through simulation.
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| 7. |
- Anh, Nguyen Tua, et al.
(författare)
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A Quantitative Method to Determine ICT Delay Requirements for Wide-Area Power System Damping Controllers
- 2015
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Ingår i: IEEE Transactions on Power Systems. - 0885-8950 .- 1558-0679. ; 30:4, s. 2023-2030
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a quantitative method to determine delay requirements of the information and communication technology (ICT) system supporting wide-area power oscillation damping (WAPOD) controllers. An allowable time delay for the ICT infrastructure named “equivalent time delay (ETD)” is defined. The ETD is calculated by numerically comparing the damping behavior of the system when local input signals (LI) and remote input signals (RI) are used in the damping controller. The use of a WAPOD is only justified when its response outperforms that of a controller using local inputs. Therefore, the total time delay in the control loop must be below the calculated ETD. As such, the ETD serves as a design criteria to determine ICT latency requirements. The selection of an effective RI signal can be carried out by considering the maximum delays (ETDs) of different wide-area measurements. A damping improvement ETDx% has been proposed using the same methodology indicating a minimum outperformance of the remote signals. The proposed method is demonstrated using the well-known Klein-Rogers-Kundur multi-machine power system and the Vietnamese power system model.
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| 8. |
- Awad, Hilmy, 1970, et al.
(författare)
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Operation of static series compensator under distorted utility conditions
- 2005
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Ingår i: IEEE Transactions on Power Systems. - 0885-8950 .- 1558-0679. ; 20:1, s. 448-457
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Tidskriftsartikel (refereegranskat)abstract
- The static series compensator (SSC) has shown a significant capability to mitigate voltage dips, which are the most severe problem to sensitive loads. Also, it has been declared that the function of the SSC can be extended to work as a series active filter. This paper proposes a moving-average filter to detect the fundamental component of the measured voltages and currents (needed to control the SSC) while using a double vector control algorithm to improve the transient performance of the SSC. This is made in order to accurately control the fundamental voltage component at the load terminals in the case of distorted grid voltage. Furthermore, a selective harmonic compensation strategy is applied to filter out the grid harmonics. The operation of the SSC under distorted utility conditions and voltage dips is discussed. The validity of the proposed controller is verified by experiments, carried out on a 10-kV SSC laboratory setup. Experimental results have shown the ability of the SSC to mitigate voltage dips and harmonics. It is also shown that the proposed controller has improved the transient performance of the SSC even under distorted utility conditions.
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| 9. |
- Bakhtiari, Hamed, et al.
(författare)
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TSO-DSO Operational Coordination Using a Look-Ahead Multi-Interval Framework
- 2022
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Ingår i: IEEE Transactions on Power Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8950 .- 1558-0679. ; , s. 1-18
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Tidskriftsartikel (refereegranskat)abstract
- With the rise of distributed energy resources and the increasing activation of flexibility resources by Distribution Systems Operators (DSOs), the Transmission System Operators (TSOs) need to co-ordinate their actions with those of the DSOs. This research uses a look-ahead multi-interval (LA-MI) framework for analyzing this coordination and explores two formulations. Firstly in the exogenous DSO model, a mixed-integer linear program is developed to reflect the pragmatic approach in many real situations whereby the TSO can only anticipate statistically the actions of the DSO. In the embedded DSO model, as a comparator, we propose a new organizational setup for the TSO-DSO operational coordination mechanism. In the resulting bilevel decomposition, a new method to calculate Benders cuts is developed and tested on a modified IEEE 118-bus test system as a transmission network and two modified IEEE 33-bus test systems as distribution networks. The benefits of the LA-MI coordination framework are substantial in comparison with the current Look-Ahead Single-Interval (LA-SI) coordination framework widely used in Europe.
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| 10. |
- Baradar, Mohamadreza, 1981-, et al.
(författare)
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A Multi-Option Unified Power Flow Approach for Hybrid AC/DC Grids Incorporating Multi-Terminal VSC-HVDC
- 2013
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Ingår i: IEEE Transactions on Power Systems. - IEEE Power system transaction on. - 0885-8950 .- 1558-0679. ; 28:3, s. 2376-2383
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a multi-option power flow approach for hybrid AC/DC grids. A unified AC-DC unit is introduced which can be used in two different cases: case a) AC grids with embedded VSC-based MTDC grids, and case b) asynchronous AC grids connected via a common VSC-based MTDC grid. In the proposed method for each MTDC grid (regardless of the number of converters), a new state variable is introduced to handle any kind of converter loss models. For the case (b), the AC-DC unit can be used in two different analyses, namely, a1) the separated analysis and a2) the integrated analysis. Both a1) and a2) can be used in the practical analysis of the real-size power systems. However, it is shown that the separated analysis not only offers a shorter computational time but it is also very suitable for the future connection between large existing AC systems and other AC systems or remote renewable energy sources through the DC grids. The proposed methodology is implemented in MATLAB software and verified using commercial software SIMPOW.
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