Showing papers on "Power-flow study published in 2016"
TL;DR: In this article, the authors consider the problem of deriving an explicit approximate solution of the nonlinear power equations that describe a balanced power distribution network and propose an approximation that is linear in the active and reactive power demands of the PQ buses.
Abstract: We consider the problem of deriving an explicit approximate solution of the nonlinear power equations that describe a balanced power distribution network. We give sufficient conditions for the existence of a practical solution to the power flow equations, and we propose an approximation that is linear in the active and reactive power demands of the PQ buses. For this approximation, which is valid for generic power line impedances and grid topology, we derive a bound on the approximation error as a function of the grid parameters. We illustrate the quality of the approximation via simulations, we show how it can also model the presence of voltage controlled (PV) buses, and we discuss how it generalizes the DC power flow model to lossy networks.
407 citations
TL;DR: Wang et al. as discussed by the authors proposed a two-stage robust optimization model to coordinate the discrete and continuous reactive power compensators and find a robust optimal solution that can hedge against any possible realization within the uncertain wind power output.
Abstract: Traditional reactive power optimization aims to minimize the total transmission losses by control reactive power compensators and transformer tap ratios, while guaranteeing the physical and operating constraints, such as voltage magnitudes and branch currents to be within their reasonable range. However, large amounts of renewable resources coming into power systems bring about great challenges to traditional planning and operation due to the stochastic nature. In most of the practical cases from China, the wind farms are centrally integrated into active distribution networks. By the use of conic relaxation based branch flow formulation, the reactive optimization problem in active distribution networks can be formulated as a mixed integer convex programming model that can be tractably dealt with. Furthermore, to address the uncertainties of wind power output, a two-stage robust optimization model is proposed to coordinate the discrete and continuous reactive power compensators and find a robust optimal solution that can hedge against any possible realization within the uncertain wind power output. Moreover, the second order cone programming-based column-and-constraint generation algorithm is employed to solve the proposed two-stage robust reactive power optimization model. Numerical results on 33-, 69- and 123-bus systems and comparison with the deterministic approach demonstrate the effectiveness of the proposed method.
290 citations
TL;DR: In this article, the use of a least mean fourth (LMF)-based algorithm for single-stage three-phase grid-integrated solar photovoltaic (SPV) system is proposed.
Abstract: This paper proposes the use of a least mean fourth (LMF)-based algorithm for single-stage three-phase grid-integrated solar photovoltaic (SPV) system. It consists of an SPV array, voltage source converter (VSC), three-phase grid, and linear/nonlinear loads. This system has an SPV array coupled with a VSC to provide three-phase active power and also acts as a static compensator for the reactive power compensation. It also conforms to an IEEE-519 standard on harmonics by improving the quality of power in the three-phase distribution network. Therefore, this system serves to provide harmonics alleviation, load balancing, power factor correction and regulating the terminal voltage at the point of common coupling. In order to increase the efficiency and maximum power to be extracted from the SPV array at varying environmental conditions, a single-stage system is used along with perturb and observe method of maximum power point tracking (MPPT) integrated with the LMF-based control technique. The proposed system is modeled and simulated using MATLAB/Simulink with available simpower system toolbox and the behaviour of the system under different loads and environmental conditions are verified experimentally on a developed system in the laboratory.
237 citations
TL;DR: In this article, the authors propose a method to optimally set the reactive power contributions of distributed energy resources (DERs) present in distribution systems with the goal of regulating bus voltages.
Abstract: In this paper, we propose a method to optimally set the reactive power contributions of distributed energy resources (DERs) present in distribution systems with the goal of regulating bus voltages. For the case when the network is balanced, we use the branch power flow modeling approach for radial power systems to formulate an optimal power flow (OPF) problem. Then, we leverage properties of the system operating conditions to relax certain nonlinear terms of this OPF, which results in a convex quadratic program (QP). To efficiently solve this QP, we propose a distributed algorithm based on the Alternating Direction Method of Multipliers (ADMM). Furthermore, we include the unbalanced three-phase formulation to extend the ideas introduced for the balanced network case. We present several case studies to demonstrate the method in unbalanced three-phase distribution systems.
231 citations
01 Jan 2016
TL;DR: The power system analysis and design is universally compatible with any devices to read and is available in the digital library an online access to it is set as public so you can get it instantly.
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222 citations
TL;DR: In this article, a unified energy flow formulation is developed to describe the nodal balance and branch flow in both systems and it is solved with the Newton-Raphson method.
220 citations
TL;DR: In this paper, the authors employ the extended Kalman filter with unknown inputs, referred to as the EKF-UI technique, for decentralized dynamic state estimation of a synchronous machine states using terminal active and reactive powers, voltage phasor and frequency measurements.
Abstract: Accurate measurement of the rotor angle and speed of synchronous generators is instrumental in developing powerful local or wide-area control and monitoring systems to enhance power grid stability and reliability. Exogenous input signals such as field voltage and mechanical torque are critical information in this context, but obtaining them raises significant logistical challenges, which in turn complicates the estimation of the generator dynamic states from easily available terminal phasor measurement unit (PMU) signals only. To overcome these issues, the authors of this paper employ the extended Kalman filter with unknown inputs, referred to as the EKF-UI technique, for decentralized dynamic state estimation of a synchronous machine states using terminal active and reactive powers, voltage phasor and frequency measurements. The formulation is fully decentralized without single-machine infinite bus (SMIB) or excitation model assumption so that only local information is required. It is demonstrated that using the decentralized EKF-UI scheme, synchronous machine states can be estimated accurately enough to enable wide-area power system stabilizers (WA-PSS) and system integrity protection schemes (SIPS). Simulation results on New-England test system, Hydro-Quebec simplified system, and Kundur network highlight the efficiency of the proposed method under fault conditions with electromagnetic transients and full-order generator models in realistic multi-machine setups.
213 citations
TL;DR: In this article, the authors proposed a simple and effective modifications to the conventional method (Newton Raphson) to compute the power flow for micro-grids, which can be easily integrated in current commercially available power system software and can be applied for power system studies.
Abstract: The study of power flow analysis for microgrids has gained importance where several methods have been proposed to solve these problems. However, these schemes are complicated and not easy to implement due to the absence of a slack bus as well as the dependence of the power on frequency as a result of the droop characteristics. This paper proposes simple and effective modifications to the conventional method (Newton Raphson) to compute the power flow for microgrids. The presented method provides a simple, easy to implement, and accurate approach to solve the power flow equations for microgrids. The proposed method is applied to two test systems: a 6-bus system and a 38-bus system. The results are compared against simulation results from PSCAD/EMTDC which validate the effectiveness of the developed method. The proposed technique can be easily integrated in current commercially available power system software and can be applied for power system studies.
202 citations
TL;DR: In this article, a unified steady-state power flow analysis considering electrical, natural gas, and district heating networks all together is presented. But the authors do not consider the impact of the different types of power flow on the performance of the units.
Abstract: This paper studies a unified steady-state power flow analysis considering electrical, natural gas, and district heating networks all together. The important reason of such a view is the increasing utilization of cogeneration plants which makes a strong coupling between these networks. Another reason is the increasing usage of district heating networks because they have a higher efficiency besides a lower carbon dioxide emission than localized boilers. In this paper, interdependencies of the mentioned infrastructures are considered in detail including a nonlinear part-load efficiency performance for units. An integrated framework based on the Newton–Raphson technique is presented to solve the combined power flow problem and several case studies are utilized to demonstrate the applicability of the proposed methodology.
175 citations
TL;DR: In this article, a probabilistic power flow analysis technique based on the stochastic response surface method is proposed to estimate the probability distributions and statistics of power flow responses without using series expansions such as the Gram-Charlier, Cornish-Fisher or Edgeworth series.
Abstract: This paper proposes a probabilistic power flow analysis technique based on the stochastic response surface method. The probability distributions and statistics of power flow responses can be accurately and efficiently estimated by the proposed method without using series expansions such as the Gram-Charlier, Cornish-Fisher, or Edgeworth series. The stochastic continuous input variables following normal distributions such as loads or non-normal distributions such as photovoltaic generation and wind power and their multiple correlations can be easily modeled. The correctness, effectiveness and adaptability of the proposed method are demonstrated by comparing the probabilistic power flow analysis results of the IEEE 14-bus and 57-bus standard test systems obtained from the proposed method, the point estimate method, and the Monte Carlo simulation method.
135 citations
TL;DR: In this article, a decentralized approach based on a modified generalized Benders decomposition in which locally optimal cost function of each area is introduced is introduced. But it is suitable for multi-area interconnected systems with a hierarchical control architecture.
Abstract: Fluctuations in wind power in geographically distributed areas are typically complementary, and therefore a coordinated multi-area dynamic economic dispatch may enable greater wind power penetration in interconnected power systems. Here we describe a decentralized approach based on a modified generalized Benders decomposition in which locally optimal cost function of each area is introduced. The technique exhibits rapid convergence and does not require parameter tuning. It is suitable for multi-area interconnected systems with a hierarchical control architecture. Comparative numerical simulations demonstrate that the performance of our method is favorable in terms of accuracy, convergence and computational efficiency. A case study on a real power system is also carried out to demonstrate the potential of this technique to increase wind power penetration.
TL;DR: In this paper, Doubly fed induction generators (DFIGs) are considered for variable speed wind farms and a method to control the output power of a wind farm with the aim of improving the transient stability of a multi-machine power system is proposed.
Abstract: This paper proposes a method to control the output power of a wind farm with the aim of improving the transient stability of a multi-machine power system. Doubly fed induction generators (DFIG) are considered for the variable speed wind farms. The variation of the frequency of the DFIG terminal bus is used to modulate the torque reference and thus the output power of the DFIG in the post-disturbance condition. This in turn modifies the electrical power of the nearby alternators and causes improvement of stability. The proposed control technique is validated in WSCC 3-machine 9-bus system and IEEE 16-machine 68-bus system. The study is carried out in PSCAD/EMTDC as well as in MATLAB platforms.
TL;DR: The theoretical foundation of the proposed algorithm, based on the well-known backward/forward sweep algorithm, conventionally employed to solve grid-connected radial load power flows, with the interesting property that they are derivative-free is shown.
Abstract: We propose an algorithm capable of solving the load power flow problem in ac droop-regulated microgrids. Based on radial distribution networks, these systems lack a slack bus for facilitating the computation by means of conventional methods. Rather than having the stiff bus that provides a voltage reference and supplies the necessary power, the voltage and power regulation must be shared among the distributed resources as a function of their frequency and voltage droop functions. The proposed algorithm is based on the well-known backward/forward sweep algorithm, conventionally employed to solve grid-connected radial load power flows, with the interesting property that they are derivative-free. We have expanded the algorithm to cope with the lack of slack bus. In this paper, we show the theoretical foundation and provide some tests with ex-post computations to investigate the coherence of the results.
TL;DR: The blackout case in the Indian power grid due to voltage collapse in the inter-regional corridor is studied, and the use of real time phasor measurement unit measurements in-order to estimate and track the oscillatory modes is highlighted.
Abstract: Major power grid blackouts in various parts of the world are characterized by voltage collapse. This paper studies the blackout case in the Indian power grid due to voltage collapse in the inter-regional corridor. First, the computer simulation models are tuned to match responses from the phasor measurement units at various locations in the grid. The inter-area mode with the frequency of 0.3 and 0.5 Hz with reduced damping were observed and resulted due to switching actions that occurred during the disturbance. This paper simulates the complex power grid network for various loading conditions of Northern region using power system simulator for engineering. Further, the system variables are analyzed using Prony method to estimate the inter-area mode for different NR loading conditions. The eigen values associated with the 0.3 Hz mode depict the movement from open left half plane into open right half plane with a slight increase in the parameter indicating “hopf bifurcation.” This paper also discusses the maximum loading capacity for the inter-regional lines in-order avoid loss of small signal stability, and highlights the use of real time phasor measurement unit measurements in-order to estimate and track the oscillatory modes.
22 May 2016
TL;DR: In this paper, the domestic and foreign standards for interconnecting distributed resources with electric power systems, and compares the contents of power quality, response to abnormal conditions, power control, voltage regulation and the ability of fault ride-through in some typical standards.
Abstract: This paper introduces the domestic and foreign standards for interconnecting distributed resources with electric power systems, and compares the contents of power quality, response to abnormal conditions, power control, voltage regulation and the ability of fault ride-through in some typical standards. Some items in wind power generation and photovoltaic power generation standards are concretely introduced. The cause of the difference between the standards is analyzed, and the development trend of the future standards for interconnecting distributed resources with electric power systems is discussed. This paper provides reference for the further improvement of the standards for grid-integration of distributed resources.
TL;DR: In this article, a linear expansion co-planning (ECP) model is proposed to minimize the overall capital and operational costs for the coupled gas and power systems, where linear formulations are introduced to deal with the nonlinear nature of the objective functions and constraints.
Abstract: In a carbon-constrained world, the continuing and rapid growth of gas-fired power generation (GPG) will lead to the increasing demand for natural gas. The reliable and affordable gas supply hence becomes an important factor to consider in power system planning. Meanwhile, the installation of GPG units should take into account not only the fuel supply constraints but also the capability of sending out the generated power. In this paper, a novel expansion co-planning (ECP) model is proposed, aiming to minimize the overall capital and operational costs for the coupled gas and power systems. Moreover, linear formulations are introduced to deal with the nonlinear nature of the objective functions and constraints. Furthermore, the physical and economic interactions between the two systems are simulated by an iterative process. The proposed linear co-planning approach is tested on a simple six-bus power system with a seven-node gas system and a modified IEEE 118-bus system with a 14-node gas system. Numerical results have demonstrated that our co-planning approach can allow systematic investigations on supporting cost-effective operating and planning decisions for power systems.
TL;DR: In this article, a three-phase linear power flow (3LPF) formulation is derived based on the fact that in a typical distribution system, voltage angles and magnitudes vary within relatively narrow boundaries.
Abstract: Power flow analysis is one of the tools that is required in most of the distribution system studies. An important characteristic of distribution systems is the load unbalance in the phases and a three-phase power flow analysis is needed. In this paper, a three-phase linear power flow (3LPF) formulation is derived based on the fact that in a typical distribution system, voltage angles and magnitudes vary within relatively narrow boundaries. The accuracy of the proposed 3LPF is verified using several test cases. Potential applications of the proposed method are in distribution systems state estimation and volt-VAR optimization.
TL;DR: In this paper, a unified, generic, and flexible power flow algorithm for isolated AC/DC HMGs is proposed, where the power flow subproblems related to AC and DC subgrids are described by a set of linear and nonlinear equations and are solved simultaneously using a Newton trust-region method.
Abstract: A promising configuration for future smart grids is an AC/DC hybrid topology that enables the integration of AC/DC energy resources and modern loads, thus permitting the consequent formation of AC/DC hybrid microgrids (HMGs). An understanding of AC/DC HMGs and their operational premise during islanding will certainly pave the way toward the realization of a future smart grid that includes a plug-and-play feature. However, the planning and operation of such isolated and hybrid systems are reliant on a powerful and efficient power flow tool. To this end, this paper proposes a novel unified, generic, and flexible power flow algorithm for isolated AC/DC HMGs. The power flow subproblems related to AC and DC subgrids are described mathematically by a set of linear and nonlinear equations and are solved simultaneously using a Newton trust-region method. The proposed algorithm is generic in the sense that it includes consideration of the unique characteristics of islanded AC/DC HMGs: a variety of possible topologies, droop controllability of the distributed resources (DRs), and bidirectionality of the power flow in the interlinking converters (ICs). The new power flow formulation is flexible and permits the easy incorporation of any changes in DR operating modes and IC control strategies. The developed algorithm was tested and applied for analyzing selected operational and control aspects of isolated AC/DC HMGs, including inaccurate power sharing and interlinking converters characterized by differing control strategies. The proposed load flow program can form the basis of and provide direction for further studies of isolated AC/DC HMGs.
TL;DR: In this paper, a multiple-time-delayed power system model is constructed with power system stabilizer (PSS) considering time-delays by using Lyapunov stability theory and linear matrix inequality (LMI) method.
Abstract: Time-delay exists widely in electric power systems, and is found to have significant effect on the performance of operation and control under certain conditions. It is shown that even a very small delay may destabilize the power system. Therefore, time-delay is of important concern and should be properly handled, especially in the wide-area measurement and control environment. However, only few results about the controller design for power system considering multiple time-delays are reported. In this paper, a multiple time-delayed power system model is constructed with power system stabilizer (PSS) considering time-delays. By using Lyapunov stability theory and linear matrix inequality (LMI) method, two $H_{\infty}$ control schemes are developed for time-varying multiple delayed systems. The proposed controllers guarantee the closed-loop system asymptotic stable with $H_{\infty}$ performance. A two-area four-machine power system and the New England 10-machine 39-bus system are employed to demonstrate the effectiveness of proposed methods. The simulation results verify that the designed controllers can improve the control performance significantly.
TL;DR: In this paper, a planning framework is proposed to find the minimum storage sizes (power and energy) at multiple locations in distribution networks to reduce curtailment from renewable distributed generation (DG), specifically wind farms, while managing congestion and voltages.
Abstract: This paper presents a planning framework to find the minimum storage sizes (power and energy) at multiple locations in distribution networks to reduce curtailment from renewable distributed generation (DG), specifically wind farms, while managing congestion and voltages. A two-stage iterative process is adopted in this framework. The first stage uses a multi-period AC optimal power flow (OPF) across the studied horizon to obtain initial storage sizes considering hourly wind and load profiles. The second stage adopts a high granularity minute-by-minute control driven by a mono-period bi-level AC OPF to tune the first-stage storage sizes according to the actual curtailment. Congestion and voltages are managed through the optimal control of storage (active and reactive power), on-load tap changers (OLTCs), DG power factor, and DG curtailment as last resort. The proposed storage planning framework is applied to a real 33-kV network from the North West of England over one week. The results highlight that by embedding high granularity control aspects into planning, it is possible to more accurately size storage facilities. Moreover, intelligent management of further flexibility (i.e., OLTCs, storage, and DG power factor control) can lead to much smaller storage capacities. This, however, depends on the required level of curtailment.
TL;DR: In this paper, an active power control strategy for multi-terminal VSC-HVDC systems tailored to enhance transient stability of hybrid AC/DC grids is proposed, which is compared to a strategy in which each VSC is controlled using only local frequency measurements of the AC side.
Abstract: Multi-terminal High Voltage Direct Current (HVDC) using Voltage Source Converters (VSC-HVDC) is a promising technology which provides flexible control of active and reactive power and facilitates remote renewable energy integration, above all using long cables. This paper analyses an active power control strategy for multi-terminal VSC-HVDC systems tailored to enhance transient stability of hybrid AC/DC grids. The proposed strategy controls each VSC using frequency measurements of all terminals. Its performance is compared to a strategy in which each VSC is controlled using only local frequency measurements of the AC side, proving that the proposed strategy shows better performance, even taking into account reasonable communication delays. The paper also shows that the proposed strategy generally gives similar results to those obtained when each VSC is controlled using the speed of the centre of inertia (COI). The speed of the COI is a more comprehensive and richer figure than the one proposed in this paper but it is also much more complex to obtain. Simulation results with PSS/E of a test system have been used to illustrate the comparisons and the main contributions of the proposal.
TL;DR: The Holomorphic Embedding Loadflow Method is shown to extend naturally to DC power transmission systems, preserving all the constructive and deterministic properties that allow it to obtain the white branch solution in an unequivocal way.
Abstract: The Holomorphic Embedding Loadflow Method is extended here from AC to DC-based systems. Through an appropriate embedding technique, the method is shown to extend naturally to DC power transmission systems, preserving all the constructive and deterministic properties that allow it to obtain the white branch solution in an unequivocal way. Its applications extend to nascent meshed HVDC networks and also to power distribution systems in more-electric vehicles, ships, aircraft, and spacecraft. In these latter areas, it is shown how the method can cleanly accommodate the higher-order nonlinearities that characterize the I-V curves of many devices. The case of a photovoltaic array feeding a constant-power load is given as an example. The extension to the general problem of finding DC operating points in electronics is also discussed, and exemplified on the diode model.
TL;DR: A novel technique for optimizing the FACTS devices, so as to maintain the voltage stability in the power transmission systems is presented and its performance is evaluated and compared with the existing GA based GSA hybrid technique.
TL;DR: In this article, a coordination framework for tie-line scheduling and power dispatch to operate multi-area systems is proposed, where wind power flows are updated hourly to hedge uncertainty in the near future, preserving the operational independence of areas.
Abstract: Large-scale wind farms are typically geographically separated from load centers and distributed in different control areas. Therefore, interregional energy dispatch is important for wind power generation via sharing spinning reserve capacity among interconnected systems. However, existing tie-line scheduling methods in China do not provide satisfactory performance in accommodating the recent large-scale integration of wind power. In this paper, we describe a coordination framework for tie-line scheduling and power dispatch to operate multi-area systems. Tie-line flows are updated hourly to hedge uncertainty in the near future, preserving the operational independence of areas. The coordinated tie-line scheduling problem is formulated using two-stage adaptive robust optimization to account for uncertainties in the available wind power and is solved using a column-and-constraint generation method in a coordinate-and-decentralize manner. Comparative simulations show that the method is effective in enabling further wind power penetration and can improve economic efficiency in multi-area systems. A case study using a large-scale power system demonstrates the benefits and scalability of the method in practice.
TL;DR: In this paper, a linear approximated methodology for full alternating current-optimal power flow (AC-OPF) is presented, which can provide more precise and real picture of full active and reactive power flow modelling, along with the voltage profile of buses compared to the commonly used direct current-optimality power flow.
Abstract: This study presents a novel linear approximated methodology for full alternating current-optimal power flow (AC-OPF). The AC-OPF can provide more precise and real picture of full active and reactive power flow modelling, along with the voltage profile of buses compared to the commonly used direct current-optimal power flow. While the AC-OPF is a non-linear programming problem, this can be transformed into a mixed-integer linear programming environment by the proposed model without loss of accuracy. The global optimality of the solution for the approximated model can be guaranteed by existing algorithms and software. The numerical results and simulations which represent the effectiveness and applicability of the proposed model are given and completely discussed in this study.
TL;DR: In this article, a multi-level energy management system (EMS) is proposed for dc microgrids operations to ensure system reliability, power quality, speed of response, and control accuracy.
Abstract: Multi-level energy management system (EMS) is proposed for dc microgrids operations to ensure system reliability, power quality, speed of response, and control accuracy in this paper. System distributed control is scheduled as the primary control. Battery energy storages (BESs) operate in voltage regulation mode with droop control for power sharing. However, bus voltage deviation and power tracking error due to line impedance are the main drawbacks of distributed control. To enhance the system power quality and control accuracy, bus voltage restoration and power sharing compensation are implemented in secondary control. Economic dispatch based on comparison of system units' marginal operation costs is carried out in tertiary control to minimize the system operation cost. Detailed elaboration has been derived to quantify BES utilization cost due to the cumulated lifetime degradation. In case of communication failure, system operation can still be retained with primary control without operating mode change so that to enhance system reliability. A lab scale dc microgrid is developed for the verification of the proposed multi-level EMS and relevant control techniques.
TL;DR: The proposed series-stacked power delivery architecture is validated with real servers performing two different real-world operations: web traffic management and computation and up to a 20x reduction in power conversion losses compared to state-of-the-art hardware.
Abstract: In this paper, an alternative method to achieve more efficient dc power distribution and voltage regulation for future data centers is presented. This paper describes a series-stacked power delivery architecture, where servers are connected electrically in series, thereby, providing inherent step down of voltage. Server voltage regulation is performed by differential power converters, which only process the mismatch power between servers. The bulk power flows with no power processing, yielding greatly increased system efficiency compared to conventional architectures. We demonstrate the series-connected architecture with an experimental proof of concept and compare the proposed architecture with a conventional dc power delivery architecture employing a best-in-class power supply unit for servers. The proposed power delivery architecture is validated with a series-stacked server rack consisting of four 12 V servers, powered from a 48 V dc bus, performing two different real-world operations: web traffic management and computation. Through experimental measurements, we demonstrate up to a 40x reduction in power conversion losses compared to state-of-the-art hardware, and an overall best-case system conversion efficiency of 99.89%.
TL;DR: In this paper, a generalised approach is proposed to model network upgrade deferral as a function of load growth rate, renewable generation penetration and peak shave fraction, which benefits from multi-period power flow analysis to co-optimise battery size, location, charge/discharge profile for a pre-specified number of units to be deployed in a given distribution network.
Abstract: Prompted by technical issues that have arisen due to the widespread deployment of distributed intermittent renewable generators, rapidly rising peak demand and reductions in battery price, the use of battery-based energy storage systems in power networks is on the rise. While battery-based energy storage has the potential to deliver technical benefits, the best possible sizing, location and usage govern the financial viability. The objective of this study is twofold. Firstly, a generalised approach is proposed to model network upgrade deferral as a function of load growth rate, renewable generation penetration and peak shave fraction. This model is then used for the formulation of an optimisation problem which benefits from multi-period power flow analysis to co-optimise battery size, location, charge/discharge profile for a pre-specified number of units to be deployed in a given distribution network. The proposed approach is implemented using the generic algebraic modelling system platform and validated on an Australian medium voltage distribution network under multiple practical and potential future scenarios.
TL;DR: In this article, a robust optimization-based AC optimal power flow (RACOPF) model for power networks with uncertain wind power generation is presented, which outperforms the robust DC-OPF model in the literature.
Abstract: This letter presents a robust optimization-based AC optimal power flow (RACOPF) model for power networks with uncertain wind power generation. Numerical results on three test systems with uncertain wind power show that the RACOPF outperforms the robust DC-OPF model in the literature.
TL;DR: In this article, a day-ahead coordinated dispatch method of reactive power is proposed to achieve optimal power flow, minimize power losses, and minimize switching of capacitor banks, in order to achieve an optimal reactive power capability of a DG.
Abstract: Reactive power outputs of DGs are used along with capacitor banks to regulate distribution network voltage. However, reactive power capability of a DG is limited by the inverter ratings and real power outputs of the DG. In order to achieve optimal power flow, minimize power losses, and minimize switching of capacitor banks, a day-ahead coordinated dispatch method of reactive power is proposed. Forecast errors of DG real power in every period are used to estimate the probability distribution of DGs reactive power capacity. Considering different output characteristics and constraints of reactive power sources, a dynamic preliminary-coarse-fine adjustment method is designed to optimize DG and shunt compensator outputs, decrease the switching cost, and reduce loss. The preliminary optimization obtains initial values, and multiple iterations between the coarse and fine optimizations are used to achieve a coordinated result. Simulations studies are performed to verify the proposed method.