1Optimal Operation of Radial Distribution Systems Using Extended Dynamic Programming
An extended dynamic programming (EDP) approach is developed to optimize the ac steady-state operation of radial electrical distribution systems (EDS). Based on the optimality principle of the recursive Hamilton-Jacobi-Bellman equations, the proposed EDP approach determines the optimal operation of the EDS by setting the values of the controllable variables at each time period. A suitable definition for the stages of the problem makes it possible to represent the optimal ac power flow of radial EDS as a dynamic programming problem, wherein the “curse of dimensionality” is a minor concern, since the number of state and control variables at each stage is low and the time complexity of the algorithm grows linearly with the number of nodes of the EDS. The proposed EDP is applied to solve the economic dispatch of the DG units installed in a radial EDS. The effectiveness and the scalability of the EDP approach is illustrated using real-scale systems and comparisons with commercial programming solvers. Finally, generalizations to consider other EDS operation problems are also discussed.
2Distribution Transformer Loss-of-Life Considering Residential Prosumers Owning Solar Shingles, High Power Fast Chargers and Second Generation Battery Energy Storage
In this study, the effect of the electric vehicle high power fast chargers in the residential sector on the aging of the distribution transformers is probabilistically quantified. This work takes into consideration the presence of the traditional rooftop solar photovoltaic panels and the most recent technology namely rooftop solar shingles used in residential prosumers (power producers and consumers). Moreover, the effectiveness of the second-generation residential home and community battery energy storage, installed in the residential prosumers and in the electric utilities premises, in preserving the distribution transformer lifetime is discussed and conclusions are drawn.
3Optimal Planning and Operation of Distribution Systems Considering Distributed Energy Resources and Automatic Reclosers
This paper presents an integrated methodology for planning and operation of distribution systems in an environment of smart grids. The decision variables considered are location and sizing of technologies such as: distributed generation (wind, solar and small scale hydroelectric), energy storage, protection elements for fault isolation and automatic reclosers for load transfer. The integration of these technologies enable a higher automation of the distribution system the which in turn brings advantages such as reduction in the energy and active power losses and improvement in the voltage profile and service quality. The methodology consists of three stages: i) a specialized genetic algorithm for location of devices, ii) a particles swarm optimization algorithm for dimensioning of elements and iii) a non-dominated sorting genetic algorithm to solve the multi-objective problem associated with the location of reclosers. The tests were performed on a system of 102 nodes to verify the performance of the proposed methodology.
4Distributed Cooperative Control and Stability Analysis of Multiple DC Electric Springs in a DC Microgrid
Recently, dc electric springs (dc-ESs) have been proposed to realize voltage regulation and power quality improvement in dc microgrids. This paper establishes a distributed cooperative control framework for multiple dc-ESs in a dc microgrid and presents the small-signal stability analysis of the system. The primary level implements a droop control to coordinate the operations of multiple dc-ESs. The secondary control is based on a consensus algorithm to regulate the dc-bus voltage reference, incorporating the state-of-charge (SOC) balance among dc-ESs. With the design, the cooperative control can achieve average dc-bus voltage consensus and maintain SOC balance among different dc-ESs using only neighbor-to-neighbor information. Furthermore, a small-signal model of a four dc-ESs system with the primary and secondary controllers is developed. The eigenvalue analysis is presented to show the effect of the communication weight on system stability. Finally, the effectiveness of the proposed control scheme and the small-signal model is verified in an islanded dc microgrid under different scenarios through simulation and experimental studies.
5A Shared Network Access Business Model for Distribution Networks
This letter proposes a new business model for distribution network operators (DNOs)-shared network access (SNA), aiming to integrate flexible demand in a cost-effective manner. The SNA scheme incentivises the incumbent DNOs to give up its exclusive access to the network, leasing the spare capacity or back up capacity to a licensed independent party. The ownership of assets will be retained by the incumbent DNO while competition will be introduced in the operation of the spare capacity. The independent parties who have license for SNA will act as secondary DNOs, tapping into the spare capacity in the network to provide flexible network services for flexible generation and demand, thus substantially reduce the network access cost for flexibility. This paper quantifies the potential benefit of mobilizing spare capacity for flexibility network usage and discusses how the proposed business model can capture such value for each player. The results demonstrate that the competition brought by the proposed SNA can take advantage of the unused capacities in the existing network assets and be able to substantially increase their capability in integrating flexible demand and generation.
6A Novel Cascading Faults Graph Based Transmission Network Vulnerability Assessment Method
This paper proposes a novel cascading faults graph (CFG) based on fault chain theory to assess the transmission network vulnerability. The proposed CFG is able to effectively reveal the mechanism of fault propagation in a transmission network by transforming an electrical network with spatial information into a fault propagation graph with temporal information, thus providing a better way for transmission network vulnerability assessment. Numerical results on IEEE 39-, 118-bus systems and French grid demonstrate the effectiveness of the proposed method.
7Distributed Nonlinear Control with Event-Triggered Communication to Achieve Current-Sharing and Voltage Regulation in DC Microgrids
A distributed nonlinear controller is presented to achieve both accurate current-sharing and voltage regulation simultaneously in dc microgrids (MGs) considering different line impedances effects among converters. Then, an improved event-triggered principle for the controller is introduced through combining the state-dependent tolerance with a nonnegative offset. In order to design the event-triggered principle and guarantee the global stability, a generalized dc MG model is proposed and proven to be positive definite, based on which Lyapunov-based approach is applied. Furthermore, considering the effects from constant power loads, the damping performance of proposed controller is further improved which is comparative with the traditional V-I droop controller. The proposed event-triggered-based communication strategy can considerably reduce the communication traffic and significantly relax the requirement for precise real-time information transmission, without sacrificing system performance. Experimental results obtained from a dc MG setup show the robustness of the new proposal under normal, communication failure and communication delay operation conditions. Finally, communication traffic under different communication strategies is compared, showing a drastic traffic reduction when using the proposed approach.
8Similarity Comparison Based High-Speed Pilot Protection for Transmission Line
To solve the following problem: the action speed of protection based on a phasor is restricted by the length of the filtering algorithm time window and the vulnerability to false data, a new pilot protection principle for transmission lines based on waveform similarity is proposed in this paper. By comparing the discrete point sets of current sampling values, a waveform similarity-based algorithm called the Hausdorff distance distinguishes the difference between both side currents of a protected transmission line, realizing fast identification, and removal of the fault. Based on the characteristics of the algorithm, setting methods and protection criterion are discussed. Finally, an improved Hausdorff distance algorithm is proposed to cope with false data. The effectiveness and advantages of the proposed algorithm are validated with theoretical analysis and extensive simulation test results.
9Optimal Decentralized Control of DC-Segmented Power Systems
DC-segmented power systems consist of AC subsystems connected to each other only by DC lines. DC-segmentation improves the transient stability and transmission capacity of power systems. Centralized control of large power systems entails burdensome communication requirements which are expensive and introduce delays. Decentralized control circumvents these problems, but finding decentralized controllers is intractable for general systems. Poset-causal systems are a special class for which the optimal neighbor-to-neighbor decentralized controller is easy to obtain. In this paper we show that DC-segmented systems are poset-causal. We observe in numerical examples that the optimal decentralized controller attains almost the same performance as the optimal centralized controller.
10Enhancing Frequency Stability of Asynchronous Grids Interconnected with HVDC Links
Frequency stability management of asynchronously interconnected grids is becoming a great challenge. This paper investigates how asynchronous sending- and receiving-end grids can be operated in a synergistic and interactive manner to guarantee frequency stability following the worst case HVDC bipole block while still ensuring operational economy. A novel enhanced frequency stability constrained multiperiod optimal power flow model (EFOPF) with flexible fast-acting HVDC corrective control is proposed. EFOPF dynamically schedules the distribution of primary reserves and HVDC corrective actions to simultaneously handle postcontingency over- and under-frequency disturbances occurring in the sending- and receiving-end grids, respectively. An alternating direction method of multipliers based distributed algorithm was developed to solve this problem. A case study of a modified two-area RTS-96 system demonstrates the effectiveness of the proposed EFOPF.
11Coordinated Dispatch of Virtual Energy Storage Systems in LV Grids for Voltage Regulation
The growth in installed solar photovoltaic (PV) capacity and the ever-increasing power demand due to the use of energy-hungry appliances have caused voltage issues. In this paper, a hierarchical dispatch strategy is proposed for coordinating multiple groups of virtual energy storage systems (VESSs), i.e., residential houses with air conditioners, to regulate voltage in low-voltage (LV) grids with high solar PV penetration. Specifically, the two levels of the proposed model are: 1) in the lower level, VESSs within each intelligent residential district are controlled locally by individual aggregator; 2) in the upper level, multiple aggregators are coordinated to achieve voltage regulation through a consensus control strategy. By exchanging information through sparse communication links, each aggregator shares the required active power adjustment among all participating groups, without compromising users' thermal comfort. Simulation result demonstrates that the proposed control scheme can effectively regulate voltage in LV grids with greater robustness and scalability.
12Multifunctional DC Electric Springs for Improving Voltage Quality of DC Grids
Electric springs (ESs) have been proposed as a distributed demand-response technology for mitigating voltage and frequency fluctuations of ac power systems fed by substantial intermittent renewable energy. This paper extends this concept to the development of DCESs for voltage regulation of emerging dc power grids. The configurations of series and shunt DCES and their respective operating modes are explained. Both types of ES and their functionalities for dc bus voltage regulation, double-line frequency harmonic compensation, and providing fault-ride-through support are discussed. The proposed DCES has been successfully applied to a 48 V dc microgrid system for experimental verification. The results show a good agreement with the theoretical analysis, confirming that the DCES can be an effective solution to provide simultaneous functions of dc microgrid bus voltage regulation.
13Stability Improvement of DC Power Systems in an All-Electric Ship Using Hybrid SMES/Battery
As the capacity of all-electric ships (AESs) increases dramatically, the sudden changes in the system load may lead to serious problems, such as voltage fluctuations of the ship power grid, increased fuel consumption, and environmental emissions. In order to reduce the effects of system load fluctuations on system efficiency, and to maintain the bus voltage, we propose a hybrid energy storage system (HESS) for use in AESs. The HESS consists of two elements: a battery for high energy density storage and a superconducting magnetic energy storage (SMES) for high power density storage. A dynamic droop control is used to control charge/discharge prioritization. Maneuvering and pulse loads are the main sources of the sudden changes in AESs. There are several types of pulse loads, including electric weapons. These types of loads need large amounts of energy and high electrical power, which makes the HESS a promising power source. Using Simulink/MATLAB, we built a model of the AES power grid integrated with an SMES/battery to show its effectiveness in improving the quality of the power grid.
14Partially Decoupled Adaptive Filter Based Multifunctional Three-Phase GPV System
This paper deals with partially decoupled adaptive Volterra filter (PDAVF) based control for a three-phase two-stage grid-interfaced photovoltaic (GPV) system. Besides maximum power extraction, the proposed control is having the potential of grid currents balancing, harmonics currents mitigation, reactive power compensation, and adaptive adjustment of DC bus voltage. The control technique is efficient in extraction of weight component of reference grid currents and an adaptation routine of filter weights uses the principle of fifth-order PDAVF with single-element observation vector implemented by using the method of least mean squares (LMS). An increased order of partial filter assures accurate estimation of filter weights by adaptive weight update at each filter step. The convergence is ensured by providing bounds on algorithm's step size. The algorithm overcomes drawbacks of Adaline-based LMS and LMF (least mean fourth) based weight estimations without imposing high computational burden. The switching losses in voltage source converter are minimized using adaptive DC bus voltage. Effectiveness of PDAVF is presented through simulation and test results. These results are found satisfactory with improved steady state and dynamic performances and total harmonic distortion of grid currents meet an IEEE-519 standard.
15Coordinated Transmission and Distribution AC Optimal Power Flow
The current separate transmission and distribution energy management system faces multiple challenges associated with integrating distributed generators (DGs) into future grids. These challenges, such as a voltage rise issue resulting in curtailment of DGs, are difficult to solve via the current separate energy management. Thus, coordination between transmission and distribution is suggested, and a coordinated transmission and distribution AC optimal power flow (TDOPF) is proposed in this paper. A mathematical TDOPF model is established and analyzed in a master-slave structure. A heterogeneous decomposition algorithm (HGD), which is inspired by heterogeneous transmission and distribution characteristics, is proposed to solve the TDOPF in a distributed manner. The HGD is compared to other typical multi-area OPF decomposition algorithms and the differences are discussed. Numerical tests verify the benefit of the TDOPF to both transmission and distribution systems. The TDOPF improves economic operations, mitigates voltage rises, and decreases boundary bus mismatches. Hence, more DGs can be accommodated by the grid. In addition, a series of numerical tests indicate that the HGD competitively solves the TDOPF.
16Design and Control of Microgrid Fed by Renewable Energy Generating Sources
This paper presents a control of a microgrid at an isolated location fed from wind and solar based hybrid energy sources. The machine used for wind energy conversion is doubly fed induction generator (DFIG) and a battery bank is connected to a common dc bus of them. A solar photovoltaic (PV) array is used to convert solar power, which is evacuated at the common dc bus of DFIG using a dc-dc boost converter in a cost effective way. The voltage and frequency are controlled through an indirect vector control of the line side converter, which is incorporated with droop characteristics. It alters the frequency set point based on the energy level of the battery, which slows down over charging or discharging of the battery. The system is also able to work when wind power source is unavailable. Both wind and solar energy blocks have maximum power point tracking (MPPT) in their control algorithm. The system is designed for complete automatic operation taking consideration of all the practical conditions. The system is also provided with a provision of external power support for the battery charging without any additional requirement. A simulation model of system is developed in MATLAB environment and simulation results are presented for various conditions, e.g., unavailability of wind or solar energies, unbalanced and nonlinear loads, and low state of charge of the battery. Finally, a prototype of the system is implemented using a 5-kW solar PV array simulator and a 3.7-kW wound rotor induction machine and experimental results are produced to reaffirm the theoretical model and design.
17Power System Operational Adequacy Evaluation with Wind Power Ramp Limits
Uncertainties associated with wind power integration challenge the operational adequacy of conventional power systems. A set of wind power ramp limits (WPRLs) is proposed in this paper to evaluate the operational adequacy of power systems with high wind power penetration and to provide operating references to wind farms in the form of a ramp power limit (RPL) and ramp rate limit (RRL). The RPL is used to evaluate the minimum and maximum allowable generation of a wind farm by considering the power reserve capacities of generators and power flow constraints of transmission lines. A robust second-order cone programming RPLs formulation with AC power flow constraints and a column-and-constraint generation based solution method are proposed to maximize the total operating range of all wind farms. Meanwhile, a Pareto optimality based RPLs evaluation approach is proposed to handle the coupled relationship among the operating ranges of the wind farms to achieve a balanced RPLs solution for each wind farm. The RRL is used to evaluate the most rapid wind power ramp behavior that can be handled by system frequency regulation without exceeding the designated frequency range. A comprehensive criterion is proposed to evaluate the RRLs by considering primary and secondary frequency regulation. Finally, the effectiveness of the proposed evaluation approach is verified through case studies.
18Energy Recycling Three-Phase Experimental Setup for Power Flow Control Devices
Power electronics grid integrated devices such as Flexible Alternating Current Transmission Systems FACTS and Custom Power devices are a very active research field. In the cases that research must be supported by experimental results, a three phase programmable voltage source and a three-phase programmable electronic load may be used to validate the device under test, but those equipment are relatively expensive for most laboratories and many laboratories in Latin-American do not have that equipment. If a laboratory has only the programmable voltage source, non-energy-recycling experiments may be performed with a passive load, with the respective cost and environmental sacrifice. This paper presents a design and a laboratory implementation of a three-phase energy recycling test bench for power flow experiments, the design features low cost and can be built with equipment available in most laboratories.
19Residential energy scheduling for variable weather solar energy based on adaptive dynamic programming
The residential energy scheduling of solar energy is an important research area of smart grid. On the demand side, factors such as household loads, storage batteries, the outside public utility grid and renewable energy resources, are combined together as a nonlinear, time-varying, indefinite and complex system, which is difficult to manage or optimize. Many nations have already applied the residential real-time pricing to balance the burden on their grid. In order to enhance electricity efficiency of the residential micro grid, this paper presents an action dependent heuristic dynamic programming (ADHDP) method to solve the residential energy scheduling problem. The highlights of this paper are listed below. First, the weather-type classification is adopted to establish three types of programming models based on the features of the solar energy. In addition, the priorities of different energy resources are set to reduce the loss of electrical energy transmissions. Second, three ADHDP-based neural networks, which can update themselves during applications, are designed to manage the flows of electricity. Third, simulation results show that the proposed scheduling method has effectively reduced the total electricity cost and improved load balancing process. The comparison with the particle swarm optimization algorithm further proves that the present method has a promising effect on energy management to save cost.
20Optimal Control Based Energy Management of Multiple Energy Storage Systems in a Microgrid
Microgrid is envisioned to be an effective framework to integrate distributed generations, energy storage systems, and various loads. As an important form of distributed generation, renewable generation may change rapidly and frequently, which poses great challenges on the management and control of microgrids. Energy storage systems are often utilized to address the intermittency of renewable generations. This paper proposes an optimal control-based energy management of multiple energy storage system to dynamically minimize the adjustment cost while keeping track of the energy storage system state of charge and maintaining the supply-demand balance in a microgrid. The proposed algorithm has taken the influences of time-of-use price, time-varying distributed generations and loads, transmission loss, energy storage system charging/discharging, and storage efficiency into account. The optimality of the proposed algorithm is guaranteed through rigorous analysis. Simulations on a 5-bus microgrid under various conditions demonstrate the effectiveness of the proposed algorithm.
21Maximum Efficiency Tracking in Inductive Power Transmission Using Both Matching Networks and Adjustable AC–DC Converters
The maximum efficiency point of an inductive power link depends on its load power consumption and the distance between the transmitter and the receiver. Matching networks (MNs) and adjustable ac–dc converters have been proposed in the literature as a means to achieve and track this maximum efficiency point. Most of the published papers in inductive power transmission only use one of these two methods without considering a joint design. In this paper, we analyze and compare both methods proposing a general joint design which exploits the advantages of each method. A proof-of-concept system was developed following the proposed flow, built and tested. This system, with a regulated output voltage, presents improvements in measured efficiencies of up to 80% (from 9.2% to 16%) at the largest distances, thus maximizing the distance range. The same approach can be used to maximize output dc voltage, instead of the link efficiency. The proposed system using our designed MN achieved a maximum output voltage that was 90% higher (from 1.36 to 2.59 V) than the case where only a step-up converter was used.
22A Control Strategy for Multi terminal DC Grids with Renewable Production and Storage Devices
This paper provides a solution for the control of multiterminal dc networks from the point of view of the network's transmission system operator, which includes local, primary, and secondary controllers. A new power flow technique is validated for this approach, which guarantees the stability and requires fewer calculations than the conventional techniques. This study also describes an optimal control strategy for intermittent (renewable) energy producers, where the controller periodically transmits information about its state to the system operator. Its main goal is to optimize economic profit for the producer. This last controller is implemented via model predictive control. The whole control strategy is validated in a scaled dc grid test-bench with four nodes. Real solar production (5 kW rated power), a storage system, as well as short-term weather and consumption forecasts are also included.
23Current Flow Controlling Hybrid DC Circuit Breaker
This paper proposes a new device by combining features of an interline dual H-bridge current flow controller with the core idea of a hybrid HVdc circuit breaker for meshed HVdc grid application. The proposed device can substitute two dc circuit breakers at a dc bus with at least two adjacent transmission lines. In addition to the current interruption action, the current in one of the adjacent lines can be controlled by the embedded current flow controller. The system-level behavior of the proposed current flow controlling hybrid dc circuit breaker is similar to that of the typical hybrid dc circuit breaker and the interline dual H-bridge current flow controller. The operation principles of the proposed device are introduced and analyzed in this work. The component ratings are compared to the existing solution, and the functionality of the proposed device is verified by simulation.
24Volt/Var Control for Power Grids with Connections of Large-Scale Wind Farms: A Review
Large-scale wind farms (LSWFs) have become a popular form of exploiting abundant wind energy. However, the integration of LSWFs presents challenges to the volt/var control (VVC) of power grids. In this regard, various VVC methods for power grids with connections of LSWFs have been proposed from different viewpoints. This paper provides a comprehensive review on VVC for power grids with connections of LSWFs. First, the challenges presented by LSWFs to VVC are investigated with regard to the uncertainty of power flow and voltage, conflicts of VVCs among interconnected power grids, operation of discrete devices, voltage stability, and reactive power market. Second, an overview on current research regarding VVC methods for LSWFs connected power grids is presented, where the VVC methods are classified into three categories: decentralized VVC, centralized VVC, and hierarchical VVC. The three categories of VVC methods are analyzed and compared in terms of their advantages, disadvantages, and applications. In addition, drawbacks of current research are concluded. Finally, to overcome the drawbacks presented in current research, this paper provides directions for future research, including event-triggered VVC methods, big data techniques, reactive power markets, energy storage systems, and VSC-based HVDC.
25Multiple-Input Configuration of Isolated Bidirectional DC–DC Converter for Power Flow Control in Combinational Battery Storage
This paper proposes a multiple-input configuration of isolated bidirectional dual active bridge dc-dc converter (MIBDC) for power flow control in combinational battery storage. It can be operated in an independent source or combinational source mode of operation to control the power transfer, with the capability of bidirectional power flow and smoother transition. The proposed configuration has the benefits of reduction in circulation power and peak current stress in an independent mode of operation, which enhances the efficiency of dual active bridge converter. It also offers a wide range of power transmission as compared to the conventional IBDC. The proposed configuration can also be used with unequal voltage level sources by connecting them in series on multi-input side. The operation and investigation of the proposed configuration are presented in detail. In addition, the strategy of power flow control with multiple-input sources is discussed. The operation of the proposed MIBDC has been verified through simulation studies using PSCAD/EMTDC and experimentally demonstrated using ARM LPC 2148 processor.
26Development of an Interactive Program to Study of the Continuation Power Flow
In this paper an interactive program developed to study of the continuation power flow is presented. Both, the graphical user interface and the power flow program have been developed in the Matlab environment thus providing a good computational performance and a users-friendly teaching software. The interactive program allows the user to edit the input and output data files of the selected power systems as well as to visualize and analyze the results directly on the computer screen. Directly from the system one-line diagram, the graphical interface allows the user change the parameters of the system (bus and lines system data); remove the transmission line clicking directly on it; view the buses voltage and angle profiles and the real and reactive power flows. In order to assess the current operating point condition, the user can also obtain the pre- and post-contingency loading margins by tracing the respective P-V curves. All these characteristics make the developed program recommended for educational purpose.
27Novel Reduced Model for Electrical Networks with Constant Power Loads
We consider a network-preserved model of power networks with proper algebraic constraints resulting from constant power loads. Both for the linear and the nonlinear differential algebraic model of the network, we derive explicit reduced models which are fully expressed in terms of ordinary differential equations. For deriving these reduced models, we introduce the “projected incidence” matrix which yields a novel decomposition of the reduced Laplacian matrix. With the help of this new matrix, we provide a complementary approach to Kron reduction, which is able to cope with constant power loads and nonlinear power flow equations.
28A Power-Frequency Controller with Resonance Frequency Tracking Capability for Inductive Power Transfer Systems
A self-tuning controller for power transfer regulation in inductive power transfer (IPT) systems is proposed in this paper. The controller enables power transfer regulation around a user-defined reference power level. The converter's efficiency is improved by constantly tuning the switching operations to the resonant current, thereby achieving the soft-switching operations reducing electromagnetic interference in the power converters. The self-tuning capability makes it ideal for dynamic IPT systems with uncertain loads and fluctuating resonance frequency. High operating frequencies can be achieved using the simplified digital circuit design for the controller, proposed in this paper, which delivers a low total propagation delay. Bidirectional power transfer can be enabled by using the proposed controller on both transmitter and receiver sides. In the reverse power flow mode, the primary converter operates as a rectifier and the power transfer is controlled through the secondary converter using the proposed controller. The performance of the proposed controller is analyzed using MATLAB/Simulink and the results are presented. Finally, the proposed controller is implemented experimentally and its performance is evaluated as a case study on an IPT system. The experimental and simulation results conform to each other, and show that the proposed converter can effectively regulate the power transfer with an improved efficiency.
29On Robust Tie-Line Scheduling in Multi-Area Power Systems
The tie-line scheduling problem in a multi-area power system seeks to optimize tie-line power flows across areas that are independently operated by different system operators (SOs). In this paper, we leverage the theory of multi-parametric linear programming to propose algorithms for optimal tie-line scheduling, respectively, within a deterministic and a robust optimization framework. Aided by a coordinator, the proposed methods are proved to converge to the optimal schedule within a finite number of iterations. A key feature of the proposed algorithms, besides their finite step convergence, is that SOs do not reveal their dispatch cost structures, network constraints, or natures of uncertainty sets to the coordinator. The performance of the algorithms is evaluated using several power system examples.
30A Mathematical Model for the Transient Stability Analysis of a Simultaneous AC–DC Power Transmission System
The outcome of recent numerical simulation shows that the conversion of an AC transmission line to a simultaneous AC-DC line improves the system stability. This paper presents a mathematical model, suitable for the stability analysis of a simultaneous AC-DC transmission system, transmitting both AC and DC powers simultaneously through an existing AC line. The model is based on the principle of equal area criterion. The salient feature of this model is the introduction of a solution technique of an integral component of the model, which avoids the trial and error approach for the analysis. The model development process considers a single machine-infinite bus system with a transmission line connecting the machine and the infinite bus. The process also considers the severe most fault at the sending end bus. The validation of the model is executed through two different approaches; comparison of the results obtained applying the proposed model to the power system with the published ones in the literature and with the results obtained using standard software, MATLAB-Simulink, based circuit simulations. The model is also applied to a realistic system and IEEE benchmark systems to verify its capability of evaluating the benefits of a simultaneous AC-DC transmission system.