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The high temperature superconducting (HTS) cable can be used as a low-voltage tie line between substations for its characteristic of high currentdensity. In this way, the remaining capacity on the low-voltage side of the transformer can be fully utilized. Moreover, The HTS cable can run in parallel with the original tie line, forming an electromagnetic ring network, to ensure the power supply of important loads. However, the short circuit current of the distribution network is large, and the electromagnetic ring network operation results in the quench of HTS cable when the short circuit fault is outside the HTS cable. It is important to ensure the safety of HTS cable under various short circuit faults. To ensure the safe operation of HTS cable in Shenzhen Power Grid, this paper built a distribution network model with HTS cable in Matlab/Simulink. The fault current and thermal process in different fault situation were analyzed. The design of fault current limiter (FCL) which is composed of the resistive superconducting fault current limiter (R-SFCL) and a shunt reactor was completed. The model of R-SFCL using R - Q method is build, and the effectiveness of the R-SFCL design is verified.

Sectionalizing switches (SSs) and tie lines play essential roles in reducing the duration of customer interruptions in electricity distribution networks. The effectiveness of such assets is strongly influenced by their placement in the grid. Operation of SSs and tie lines is also inherently interdependent. Due to the structural complexities regarding the mathematical modeling of such dependencies, optimization of the planning and operation of switches and tie lines has typically required either leveraging heuristic and metaheuristic approaches or oversimplifying the network topology. To tackle such issues, this paper presents a computationally-efficient model for reliability-oriented concurrent switch and tie line placement in distribution networks with complex topologies. The proposed model can be applied to grids with several tie lines and laterals per feeder, and yields the optimal location of tie lines, type of tie switches, namely manual or remote-controlled, and the location and type of SSs. Being cast as a mixed integer linear programming (MILP) problem, the model can be efficiently solved with guaranteed convergence to global optimality using off-the-shelf optimization software. The efficiency and scalability of the proposed model are demonstrated through implementation on five networks and the outcomes are thoroughly discussed.

A tie-line security region provides all possible tie-line power injections with which constraints in a regional network will not be violated. With the high penetration of renewables, a sharp increase or decrease of renewable power requires a good depiction of the tie-line security region considering time coupling. However, the tie-line power security region with time coupling is a high-dimension polytope, which leads to a considerable computational burden. This paper presents a fast algorithm to approximate the original high-dimension tie-line security region considering time coupling. A few lower-dimension polytopes associated with combinations of different periods are calculated for the approximation. An evaluation method with clear physical explanations is established to measure the accuracy of the approximation. The method converts the evaluation to two linear programming problems based on the mathematical relationship between optimal points and polytope vertices. Under a Monte Carlo framework, the statistical analysis is employed to measure the accuracy using five presented indices. The performance of the proposed methods is verified by the case studies on the IEEE 118-bus test system and a 661-bus utility system.

This article deals with the Automatic Generation Control (AGC) mechanism for an interconnected, deregulated hybrid power system. The physical generation constraints such as boiler dynamics, governor dead band (GDB) and generation rate constraints (GRC) are included for a more realistic approach. The integration of distributed generation (DG) systems is also considered to match with present scenario. The intermittency nature of the DGs ruins the system's inertia and dynamic behaviour. A novel cascaded fractional order controller configuration 2-DOF (FOPIλDN)-PDN is proposed for the AGC mechanism and a new quasi opposition based volleyball premier league (QVPL) algorithm is employed to optimize the controller gains. On the other hand, the inertia emulation strategy (IES) based modified HVDC tie-line is used parallel to the AC tie-line to retrace the power system's inertia. The impact of the proposed controller and IES based modified HVDC tie-line has been analysed by subjecting to several case studies. The effectiveness of the QVPL based proposed controller has also been tested by comparing it with the previously published works on the same platform.

Interconnection of two autonomous swarm grids (DC clusters) which are designed for energy access can increase power supply availability for power hungry appliances such as water pumps. Here, a surplus or a deficit power in one cluster is balanced by a second cluster through power exchange. Usually, the clusters are connected by a tie line if bus voltages in both clusters are equal and constant. If the bus voltages are different and constant, a single converter is used to interconnect the clusters and to control the power flow between them. In both interconnections, power flow is triggered by bus voltage variations from their constant values. However, if the bus voltages are different and are not constant, the coordination of the power exchange between the clusters is a challenge. In this paper, two buck-boost converters are proposed to interconnect the clusters that have different and unregulated bus voltages. To control the power exchange while reducing transmission line loss, a decentralized control approach which is composed of a voltage droop control method and a mid-point voltage control method is proposed. Simulations of two interconnected clusters carried out in MATLAB/Simulink software show how the proposed control method can efficiently coordinate the power exchange.

The short-circuit current characteristics fed by the renewable energy source are quite different from those of the synchronous generator, which may lead to the phase selection error or failure of the traditional fault phase selection component, and then affect the operating reliability of the distance protection and the automatic reclosing. This study analyses the existing issues in the application of traditional phase selection components to the tie-line of renewable energy power, according to the fault characteristics of different renewable energy sources such as photovoltaic power source, direct-drive wind turbine and doubly-fed wind turbine. Furthermore, the sequence voltage expressions in the case of different types of faults, which takes account of the influence of the renewable energy type and the transition resistance, are theoretically derived. Hereby, a novel phase selection method by using sequence-voltage phase comparison and phase-voltage amplitude comparison is proposed. This method is applicable to the tie line of different types of renewable energy power station, and possesses the superiorities of high reliability and strong tolerance towards large fault transition resistance. Digital simulation results verify the favourable performance of the proposed method.

With the increase in wind power penetration, wind power ramping events have increasingly influenced tie line power control in the power grid. Large power changes during ramping events make it difficult to accurately track the scheduling plans of tie lines and can even lead to overrun. Determining how to evaluate the control performance of automatic generation control (AGC) for wind power ramping has become an urgent problem. In this context, this paper studies the control performance of AGC for wind power ramping based on deep reinforcement learning. First, a tie line power control model of a power system with an AGC module is established. Then, measured data, which include thermal power, wind power, hydropower output and tie line power data, and a deep reinforcement learning method are combined for AGC parameter estimation based on the deep Q-network (DQN) algorithm. Next, the AGC parameter in different scenarios are fit by using measured phasor measurement unit (PMU) data, and on the basis of the fitted model, AGC performance evaluation is performed for wind power ramping events. Finally, the simulation results verify the feasibility and effectiveness of analysing the relationship between wind power ramping and AGC performance based on the AGC parameter fitting model.

This paper investigates the problem of how to effectively smooth the short-term tie-line power fluctuations for grid-connected industrial microgrids (IMGs) from demand side. A wide-area closed-loop control architecture is proposed by directly and continuously modulating load power consumption, e.g., the aluminum electrolysis load. To optimally design the load smoothing controllers, an output regulation approach combined with LQ optimal control is developed. In particular, dominant frequencies of wind power fluctuations are analyzed and incorporated into the exogenous system that models time-varying disturbances. Simulations are conducted for a real industrial microgrid in the Inner Mongolia, China, to validate the practical feasibility and effectiveness of the proposed smoothing control strategy. It is demonstrated that the demand side control based on output regulation is able to achieve not only zero steady error in rejecting the time-varying wind power disturbance but also guarantee the satisfactory dynamic performance of modulated loads for the grid-connected IMG.

Electrical power networks usually consist of multi-area systems, which are connected by tie lines. Dynamic economic/environmental dispatch of multi-area approaches are used to schedule such networks. The goal of multi-area scheduling is determining the optimal operation of generation units and the tie line power flow in a certain period by minimizing environmental constraints. Such operation problem is limited by technical constraints of thermal generation units, tie line constraints, and transmission losses. A major limitation of multi-area economic/environmental dispatch problem is the capacity of tie lines. The worst scenario of weather condition is generally employed to set this capacity. This value is called static line rating (SLR). However, the SLR is less than the real-time capacity of overhead line. The capacity of overhead line can be determined by estimation of weather condition data for better utilization of overhead lines. This value is called dynamic line rating (DLR). In this paper, a decentralized methodology is proposed for optimal scheduling generation units taking into consideration environmental constraint, dynamic line rating, wind power generations; compressed air energy storage and power pool market. The e-constraint approach is applied to solve proposed dynamic economic/environmental dispatch of multi-area model. In addition, a fuzzy satisfying technique is used to select the best compromise solution. An interconnected, multi-area power system with cross-border trading in the presence of wind power uncertainty and the storage unit is considered for evaluating the proposed method. The proposed decentralized approach is based on the integrated simplicial decomposition method (SDM), the nonlinear block Gauss-Seidel (GS) method and the augmented Lagrangian method (ALM) (SDM-GS-ALM) decomposition algorithm, because we need to schedule a multi-area network without central operation intervention.

Phase change materials along the GeTe-Sb isoelectronic tie line are proved to be promising host material for optimization, based on which the well-known golden composition is developed. Here, Sc doped Ge2Sb1Te2 has been proposed for phase change memory (PCM) application, showing higher thermal stability and faster operation speed than those of the golden composition. The fast speed of 40 ns, high 10-year data retention of 160 °C, and good endurance of 6×105 cycles have made Sc0.2Ge2Sb1Te2 a promising candidate for PCM application. The impact of Sc on the microstructure is believed to be essential for those improvements in PCM.

For a large interconnected power system, the connections between subsystems are getting closer. The influence of the external area (EA) must be considered when the reliability of the internal area (IA) is analyzed. The equivalent method is widely used in the reliability analysis of interconnected power systems to improve the efficiency of evaluation. This paper proposes a high-accuracy tie-line probabilistic feasible region equivalent model, which replaces the traditional network flow method with the multi-objective optimal power flow. Based on the “not loss of load sharing agreement”, the feasible region states of the equivalent tie line are combined to further simplify the reliability assessment. Simulation results of IEEE 9-bus and IEEE-118 bus systems demonstrate the efficiency and accuracy of the proposed equivalent model and its effectiveness in reliability assessment.

This article briefs about an evaluation of dynamic impact of capacitive energy storage (CES) in load frequency control (LFC) in a renewable energy based three area power system. The proposed power system model consists of Thermal and solar thermal power plant in area 1, Thermal and wind plant in area 2, Thermal and Photovoltaic plant in area 3. The areas are interconnected through AC/DC tie line. In this study nonlinearities such as governor dead band and generation rate constraints are considered for thermal generating unit. Tilted-integral-derivative with filter (TIDF) controller is taken as a secondary controller. The system dynamic responses such a frequency deviation, tie power deviation and settling time of the proposed system are compared with and without CES with different types of controller. The simulated results showed that with the coordinated action of CES with proposed secondary controller the system dynamic performances have improved.

This document presents the execution of distributed generation (DG) resources in case of load frequency control (LFC) for three-area multi-source power systems. The DG system by way of a well-coordinated control can significantly progress the stability of the system frequency. Tilted integral derivative (TID) controller is projected here for controlling the objective function. Dynamics values are compared between the differential evolution particle swarm optimization (DEPSO) and teaching-learning-based optimization (TLBO) techniques using TID controller using MATLAB/SIMULINK through numerous simulations. TLBO based three-area system outperforms the DEPSO base system. The system dynamics are enhanced by using DC link to this existing alternating current tie line.

Nowadays, the resilience enhancement is one of the most important concerns in electric power networks. The division of the main microgrid into several sub-microgrids, i.e., microgrid formation (MF), is a resilient strategy for distribution systems against natural disasters and cyber-physical attacks. Such effective solution not only increases the resilience and load restoration but also reduces the costs. The extensive penetration of renewable resources in microgrids increases the issues about safe operation under faults. This chapter presents a resilient microgrid formation in the presence of solar, wind, and diesel Distributed generation (DG) for load restoration maximization. In order to carry out the microgrid formation, several candidate breakers and tie-line switches are considered, and their optimal on-off conditions are determined. Both the active and reactive powers are included in the model. The model is expressed as mixed-integer linear programming (MILP) and is simulated under three various cases including case 1, without formation strategy; case 2, formation strategy with line breaker switch; and case 3, formation strategy with both line and tie breaker switches. The numerical results are carried out based on IEEE 33-bus and 69-bus standard distribution networks. The results emphasize on the effectiveness of the developed formation strategy with both the breaker and tie line switches for load restoration and resilience enhancement. 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG. Scopus 2-s2.0-85107857635

In order to cope with the rapid development of renewable energy in the Northwest Power Grid, it is an urgent need to predict the renewable energy consumption capacity and transaction needs of the provinces, and promote the timely consumption of renewable energy within and between provinces. Therefore, this paper proposes a real-time transaction prediction method based on the generalized tie-line. Based on the definition of generalized tie lines, a multi-objective optimization model is established. The optimization objectives include positive and negative reserve of the provincial power grid and generalized positive and negative reserve of the main and sub-control areas. The method analyzes the power transmission and reception capacity and power transmission and reception needs of the main and sub-control areas in the next few hours, calculates the power purchase and sales capacity among the provinces, and automatically generates intra-provincial replacement and inter-provincial transaction plan based on the transaction rule library to enhance the intelligence level of renewable energy consumption in the Northwest Power Grid.

In order to improve the utilization efficiency of wind energy and reduce the wind energy curtailment as much as possible, this paper proposes an active power control strategy based on peaking and tie line constraints, which divides peaking and tie line absorptive capacity into dynamic zones. Through flexible switching of control modes in different zones, the utilization of peaking and tie line capacity can be maximized. Considering the situation that there is the non-energy dissipation of power grid due to peak load regulation or blocked cross-section, this paper proposes an echelon active power control strategy, taken into account the utilization of hours and the completion of trading power, thus, ensuring the fairness of the generating capacity of each station. The practical operation on a power grid system of northern part China demonstrates the feasibility of the proposed method.

The authors in this paper formulated mathematical equations of Multi-area Economic load dispatch in conventional approach. Multi-area Economic load dispatch problem is a vital issue in power system scheduling, processing, organizing and managing. MAELD issue in power system is explored with the combination of electric utilities of various different regions. The mathematical formulation of multi area dynamic dispatch problem in view of real power and tie-line limits have been explained in this paper. This work of mathematical formulation will be useful for the research work on multi-area economic load dispatch problems with electric vehicles (EVs) and Renewable Energy Sources (RES).

Thermostatically controlled loads (TCLs) are regarded as one of the promising resources for suppressing power fluctuations due to renewable energy (RENs). However, due to the great burdens of fully considering each users’ characteristics, it is difficult to achieve unity of the individual optimal decisions and global optimum in demand-side management (DSM). This paper proposes a game-theoretic DSM that can optimize the global power consumption schedule by individual TCL user's optimization. By integrating the prediction of REN outputs into the pricing mechanism, the proposed DSM can guide the users to make their best power consumption schedules along with intermittent REN generations, thus to smooth the tie-line power of microgrids. In this paper, a novel pricing mechanism is firstly developed based on the concave N-person game theory, which is more adaptive and flexible compared with existing game-theoretic DSM. Then, an individual's power consumption optimization and its simplified model are developed considering the constraints of the TCL model and personal preferences. The simplified model can be easily solved and achieve a fast solution in the power consumption game. An implementation framework of the proposed DSM is further developed for practical application. Finally, numerical studies verify the effectiveness of the proposed models and methods.

Radiation from the sun is an amount that is produced each hour by the Sun and is a critical information for the outline and decide the productivity of a photovoltaic plant and ambient temperature enormously influence the execution of the solar power. In this paper a new approach is projected for analysis on style and control of grid solar system the project is based on power control of tie line. This technique of low stress on utilization of customized control topology. The working principle of described method is that the grid is developed by the solar system for the distribution of energy and tie line control is developed with the help of two parameters viz. frequency and power. For obtaining this we are using here maximum power point tracking (mppt) and boost converter for increasing the efficiency of photovoltaic cell. In every PV system MPPT is a pivotal technique. From the results it is clear that the presented techniques of control using mppt can ward off tracking differences and gives an enhanced outcome in both steady and dynamic response.

This article presents the impact of various renewables and ESD on three- area LFC system. Area-1 contains thermal-DSTS-STPP systems and area-2, 3 comprises of thermal systems only. An initial effort was made to apply cascade PI-TID as an ancillary controller with crow-search algorithm (CA) as an optimization technique in LFC studies. Comparison of system dynamics with PI-TID controller in a thermal system are compared with PID, TID reveals the better performance. It is observed that integration of renewable like STPP and DSTS in area-1 improves system dynamics over thermal alone. Moreover, it is also observed that system dynamics improves with ESD like RFB and UC. Further, studies are also conducted with HVDC tie-line and show better performance over AC tie-line. Furthermore, the optimal location of AC-HVDC tie-line is found in the area among the disturbance connected areas.

When the transmission power of UHVDC line or provincial AC tie line drops sharply, the power storage station at the grid side is connected to the fine cutting system because of its fast power response characteristics, and it provides support for the safe and stable operation of the main network through the timely switching of the whole station operation mode. In this paper, the composition and operation principle of the battery storage power station on the grid side are analyzed comprehensively, and the emergency control system architecture, strategy and test method of the storage power station are analyzed in depth, hoping to provide useful reference for relevant practitioners.

Tie-line scheduling in an interconnected power grid is difficult to perform optimization by establishing a unified physical model due to the different scheduling methods in different dispatching centers. It may cause repeated coordination and iteration in multi-level dispatching centers. Therefore, a data-driven tie-line scheduling method with self-learning ability is proposed. First, perform cluster pre-processing of historical dispatching data with K-means algorithm; secondly, establish a deep learning model of tie-line scheduling based on long short-term memory (LSTM), and build a mapping model among system load, clean energy output and tie-line schedule through historical data training; After that, the all above process is used as a foundation to do the tie-line scheduling; finally, continuously revise the model by accumulating historical data, so that it has the ability of self-evolution and self-learning. We make a case analysis based on the actual power grid data, and the calculation results show the effectiveness of the proposed method.

In automatic generation control (AGC), the determination of frequency deviation coefficient under the mode of tie line bias control (TBC) plays an important role in the control system stability and frequency recovery. Based on the analysis of the actual operation of AGC, this paper presents a method to determine the frequency deviation coefficient. Firstly, considering the limitation of current automation level, a frequency deviation coefficient model for all-day multiperiod under different operating modes is established according to the frequency response characteristic of power system. Then, in order to meet the requirements for frequency recovery in the actual power grid, a strategy to modify the frequency deviation coefficient according to the frequency deviation is proposed. Finally, due to the continuous improvement of the penetration rate of new energy in the power system, this paper also considered the influence of wind power in the load frequency control system (LFC) model. The effectiveness of the method is verified by the simulation results of two areas interconnected power system.

The joint operation of natural gas system and power system is an important direction of energy system integration. In this paper, the unit combination modeling method of integrated gas-electric energy system is studied, and the operation constraints such as output, climbing and duration considering unit startup and shutdown state are established. The matrix balance model of power system and natural gas system is established. Based on the generation transfer distribution factor, the tie line security constraints are proposed, and the simplified method of gas electric coupling model of gas turbine based on the piecewise linearization method is proposed. Finally, 6-node power system and 6-node natural gas system are used to build an integrated gas electric energy system. Taking the economic cost optimization as the optimization goal, it is verified that the unit combination constraint in this paper can effectively optimize the unit operation dispatching in the combined system.

It is benefit to connect different substations from the low voltage side by high temperature superconducting (HTS) cable to make full use of the remaining capacity of the transformer. Meanwhile, if necessary, the HTS cable can form an electromagnetic ring network with the original tie line to improve the power supply reliability. However, the short circuit fault at adjacent components of the HTS cable during closed loop operation may also cause the quench of the HTS cable, which brings difficulties to the protection of the HTS cable. Based on the actual project of HTS cable in Shenzhen Power Grid, this paper calculates the fault current flowing through the HTS cable in different operation modes. The parameter requirements of the resistance superconducting fault current limiter (RSFCL) are analyzed, and the design of the RSFCL is completed. The system with HTS cable and RSFCL was modeled in detail in Matlab software, and the effectiveness of the RSFCL design is verified.

High Voltage Direct Current Transmission (HVDC) technology with large transmission capacity, flexible regulation and low loss is an important means to solve the uneven distribution of renewable energy and load centers in China. The current optimal dispatching model of HVDC tie-line only considers the consumption and cost of new energy in sending power grid which ignores the peak demand of the receiving power grid. To this end, a new HVDC tie-line optimal dispatching decision process combined with peak load regulation margin constraints of receiving power grid has been studied, and a modified brain storm algorithm (MBSO) is proposed to solve the model. Finally, the proposed model is tested and compared with conventional dispatching models on two regions in China to verify its effectiveness.

The growing demand for electric energy and the increasing penetration rate of renewable energy sources have led to the development of regional electricity markets internationally. In this paper, decentralized power exchange scheduling methods are discussed, in terms of tie-lines of interconnected areas, where each area has a separate electricity market. These methods include auxiliary problem principle (APP), optimality condition decomposition (OCD) and alternative direction multiplier (ADM), and it has been tried to compare different aspects of the operation to identify their efficacy under different conditions. The comparisons made in this paper are more comprehensive than previous studies and it has been tried to identify the positive aspects and challenges of each method with respect to network conditions and the superior method for coordinated scheduling of the tie-lines is determined. Simulation studies have been performed on a three-area (triangular structure) test system to create a loop between the intersecting tie-lines. Also, different tie-line capacities between the areas and different choice of references buses are considered. The efficacy of these methods in each case is described.

The interconnection of sub-regions through tie lines can improve the overall economy of the system and provide a broad space for renewable energy consumption, such as wind power. However, at present, no detailed models exist for tie lines in the planning of multi-area power systems. In this paper, a novel multi-area and multi-objective model for the generation, transmission, and battery energy storage systems expansion planning is proposed in a central planning method that considers uncertainties of wind power and load. Tie lines among different subareas are used as support power sources, and detailed tie-line expansion planning models that consider the power flow direction, degree of power flow fluctuation, and number of power flow direction reversal in the tie line are presented to make the model more realistic. Besides, short-term operation problems (i.e., unit commitment) are incorporated in the long term planning issues to improve the adaptability of planning schemes. Linearized procedure for the different tie-line operation modes is implemented in order to improve the efficiency of the presented model. The proposed model is finally transformed into a mixedinteger linear programming formulation. The modified IEEE RTS-24 bus system is conducted to evaluate the practicality and effectiveness of the proposed method.

The use of high temperature superconducting (HTS) cable as tie line between stations can effectively improve the reliability of distribution network. The access of HTS cable will inevitably affect the power flow of the system, thus the power system may not operate safely and economically. In an actual distribution network with HTS cable, this paper establishes distribution network model around the access point of HTS cable. The power flow under various operating modes of the distribution network is calculated. With the network loss and voltage deviation as the objective function, the discrete particle swarm optimization (DPSO) is used to optimize the power flow. Optimization is well implemented in the distribution network.

Tie-line power exchanges play an important role in promoting the optimal utilization of power resources in interconnected power networks. An accurate description of a tie-line power transfer region guarantees the optimality and security of system operations. This paper proposes a unified method based on multi-parametric programming to capture an exact tie-line power transfer region in interconnected power networks. Different types of tie lines, including AC tie lines, DC tie lines and mixed AC-DC tie lines, can be incorporated. Furthermore, the properties of the tie-line power transfer region is analyzed. The impacts of the tie-line types and the electrical distance on the tie-line power transfer region are discussed.

With the rapid development of microgrid, its tie-line switching from grid-connected to islanded mode is a topic worth discussing for considering both main grid resilience and microgrid security. In this paper, a stochastic security-constrained optimal power flow (OPF) method is proposed to deal with these conditions under high uncertainties. Firstly, a linear load flow model and a backward forward sweep algorithm are applied to present microgrid power flow with reduced computing burdens. Secondly, with consideration of tie-line switching from grid-connected to islanded operation mode, a security-constrained OPF problem for a microgrid is proposed to minimize operating cost and by optimizing microturbine setpoints and load shedding coefficient. To promise stable islanded operation after disconnection from the main grid, a Benders decomposition method is developed to decouple the OPF problem into a grid-connected master problem and an islanded sub-problem and then solve them iteratively with Benders cuts to guarantee microgrid security after tie-line switching. Last, a stochastic optimization method with probabilistic modelling is adopted to address the uncertainty issue caused by renewable energy sources and loads. The proposed stochastic security-constrained OPF method has been verified with high computing efficiency and robust security via comprehensive numerical simulations.

In this paper, a novel hybrid chemical reaction optimisation and particle swarm optimisation (HCROPSO) optimised PI controller has been proposed for automatic generation control (AGC) problem. A two area reheat thermal-hydro system with non-linearities such as governor dead band (GDB), generation rate constraints (GRC) and boiler dynamics is considered. The parameters of PI controller are optimised employing HCRO-PSO technique. The superiority of the proposed approach is shown by comparing the results with PSO, CRO and fuzzy logic control (FLC). Improvement in system performance is obtained in terms of reduced settling time, overshoot and undershoot of frequency deviation and tie line power deviation with proposed controller. Investigation is performed with variation in inter rate and inertia weight parameters. Sensitivity analysis is performed by varying the system parameters and generation rate constraints from their nominal values. Analysis reveals that HCRO-PSO optimized PI gains obtained at nominal are quite robust and need not be reset for wide changes in system parameters. Keywords: Chemical reaction optimisation (CRO), Particle swarm optimisation (PSO), Governor dead band (GDB), Generation rate constraints (GRC)

With the increase of the permeability of renewable energy in the power system, there are more and more difficulties to control the load frequency of the regional power grid. The access of large-scale new energy sources has an impact on the frequency deviation of the power system. This problem is more serious in small-capacity regional power grids that are weakly connected to the main power grid. Considers the characteristics of different types of renewable energy units, this paper establishes a physical model of interconnected power systems with multiple generator sets, and simultaneously establishes a mathematical model of coordinated control of regional grid load frequency. Based on the Nash equilibrium principle, the Solutions can be easily found. The method realizes coordinated control of AGC and AVC by adjusting the output of the unit to reduce system frequency deviation and tie line power deviation caused by renewable energy access.

Future energy descent systems will be expected to be controlled by the using of renewable power sources of which wind energy is one of the favorable sources. This paper treats with the implantation of genetic algorithms for making the parameters needed for PID applied to interconnected thermal and hydraulic power systems at best use and most effective. Two-areas of hydraulic and thermal power systems with wind connected parallel to each one are considered to exemplify the effective parameter investigation. First hydraulic and thermal are connected with tie line with the wind connected parallel to hydraulic or thermal, and then disturbance was made at thermal power plant, then to hydraulic power plant. Simulations are performed aided by the integrated Simulink/Matlab environment taking into consideration the genetic optimization process. Multiple integral representations variables with different cost functions were considered in the search for the effective AGC parameters. The outcomes established by this paper shows the impact of the genetic algorithms for LFC about multiple areas connected power systems based on different wind power using in the tuning of such a process.

In future active distribution networks (ADNs), microgrids (MGs) may have the possibility to control the power dispatched to the ADN by coordinating the output power of their multiple renewable generation units and energy storage units (ESUs). In this way, each MG may support the active distribution network, while promoting the penetration of renewable energy sources in a rational way. In this paper, we propose a tie-line power flow control of a hybrid MG, including photovoltaic (PV) generator, small wind turbines (WT), and ESUs.Firstly, the structure of the hybrid PV/WT/ESU MG is presented. In this power architecture, the battery is directly connected to the PV side through a DC/DC converter, thus reducing the number of conversions. Secondly, a hierarchical control is proposed to coordinate all those elements of the MG, making the tie-line power flow constant for a period of time, e.g. 15. min. Also, a method to calculate the tie-line power flow to be exchanged between the MG and the ADN is explored, and a power ramp rate is given between different dispatch intervals. Finally, a simulation model of the hybrid MG is built and tested. Simulation results show that the proposed hierarchical control strategy can select the proper operational mode and achieve seamless transfer between different modes. It also presents power curtailment functionality when the difference between the WT/PV output power and tie-line exchanged power flow is too large.

When a fault occurs in the power grid, voltage-source converter high-voltage direct current (VSC-HVDC) connected offshore wind power plants (OWPP) will enter the fault ride-through operation state under the control of wind turbines and modular multilevel converters. The adverse effects of its complex fault current characteristics on power grid protection are highlighted. According to the topological structure and control strategies of OWPP, a theoretical calculation method for OWPP’s fault current under symmetric and asymmetric faults is proposed. On this basis, this paper comprehensively studies the applicability of distance protection on the tie line of OWPP, analyzes the existing problems, and gives corresponding engineering solutions. The correctness of the analysis conclusions is verified by digital simulation results.

Chalcogenide phase-change materials (PCMs) based random access memory (PCRAM) enter the global memory market as storage-class memory (SCM), holding great promise for future neuro-inspired computing and non-volatile photonic applications. The thermal stability of the amorphous phase of PCMs is a demanding property requiring further improvement. In this work, we focus on indium, an alloying ingredient extensively exploited in PCMs. Starting from the prototype GeTe alloy, we incorporated indium to form three typical compositions along the InTe-GeTe tie line: InGe3Te4, InGeTe2 and In3GeTe4. The evolution of structural details, and the optical properties of the three In-Ge-Te alloys in amorphous and crystalline form, was thoroughly analyzed via ab initio calculations. This study proposes a chemical composition possessing both improved thermal stability and sizable optical contrast for PCM-based non-volatile photonic applications.

This paper proposes the participation of the virtual inertia of wind generation in the control of load frequency and damping of oscillations in interconnection lines. The proposed approach considers high penetration of Wind Farm Power Plant (WFPP) connected to hydro generation area. Virtual wind inertia has been widely investigated to control frequency in an interconnected system. As the WFPP is usually connected to the grid through static converters, they can act quickly to provide the Load Frequency Control (LFC) with fast dynamics. Therefore, the main idea is to include an additional fast control action with the objective of aiding the frequency stabilization to damp oscillations in interchange power line. It seeks to reduce the inverse response of hydro power plant and maintain a scheduled wind power. A hydro-wind power system is used to show the effectiveness of the proposed approach.

Active power balance and frequency control are important tasks in the daily management of a power system. With the integration of several microgrids in the modern power system, the balancing of sou...

Simultaneous tuning of conventional secondary controller along with different energy storage devices is presented in this paper. For each generating unit of an interconnected power system, in addition to primary control, a secondary controller is placed to reduce the frequency oscillations and to control power flow between the areas which are interconnected together. In this paper, along with the secondary controllers, energy storage devices are placed for better control of system frequency and tie line powers. Particle swarm optimization algorithm is chosen for obtaining proper control parameters for both units. Later, the effect of these additional components is compared with the conventional two area interconnected power system. Simulation studies are carried out in MATLAB-SIMULINK.

This paper presents both application and comparison of the metaheuristic techniques to multi-area economic dispatch (MAED) problem with tie line constraints considering transmission losses, multiple fuels, valve-point loading and prohibited operating zones. The metaheuristic techniques such as differential evolution, evolutionary programming, genetic algorithm and simulated annealing are applied to solve MAED problem. These metaheuristic techniques for MAED problem are evaluated on three different test systems, both small and large, involving varying degree of complexity and the results are compared against each other.

Modern power grids, especially high-voltage grids, are increasingly integrated with wind farms. The correct action of distance protection for the wind farm tie line plays an important role in the safe and stable operation of the power system. However, based on the fault characteristics of wind farms based on the doubly fed induction generator, considering crowbar action and weak infeed properties, this paper reveals some serious defects of conventional distance protection. The result shows that, due to the influences of mixed data window and damped current component with near-rotor-speed frequency, the fault distance calculation result obtained by the fundamental-component-based distance protection is inaccurate. To tackle this problem, a transient-based distance protection countermeasure along with a faulted phase selection technique is proposed. Specifically, the transient phase voltage characteristic for different fault types is analyzed to select the faulted phase. Considering the effect of high-frequency components, pre-fault voltage compensation, and transducer characteristics, a distance calculation procedure including a low-pass filter, the reconstruction of voltage at the fault point, and an iterative fault distance calculation is proposed. The comprehensive performance of the proposed method is validated by the simulation case studies using the PSCAD/EMTDC software. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Tie-line scheduling (TS) becomes a practical need for growing interconnection of regional power grids and the increasing integration of renewable energy. In electricity markets without a coordination organization, TS should be handled in a fully decentralized manner, where the impact of contingencies should also be considered for operational reliability. In this paper, the contingency-constrained TS (CCTS) problem is formulated using a two-stage robust optimization (RO) scheme to consider the $N-k$ security criterion. This robust model is decomposed and handled by the alternating direction multiplier method (ADMM) in a fully decentralized way, where the column-and-constraint generation (C&CG) is incorporated to solve the regional robust subproblems. Three computational strategies are also developed to enhance the computation efficiency of the decentralized algorithm. Numerical simulations are given to study the computational performance, the solution quality, and scalability of the proposed method.

With the large-scale integration of wind power with extremely high volatility, the transmission lines in high proportion wind power grid often present high power peak-valley difference and low transmission efficiency. In order to solve this problem, this paper puts forward an idea of improving the power of tie-lines by partition and layering. The proposed tie-line power characteristic index is used to partition the power grid, and the tie-line between partitions with large power peak-valley difference and low transmission efficiency in the scheduling period becomes an object to be optimized. Based on the partition, an inter-partition and intra-partition bi-level programming model is established. The upper model is solved with the objective of minimizing the peak-valley difference and maximizing transmission efficiency of expected power; The lower model introduces the source-load operation constraints within the partition to find the source-load coordination scheduling plan that can realize the expected power of the tie-line to the greatest extent. Python is used to program multi-objective genetic algorithm and single-objective genetic algorithm that are used to iteratively solve the upper and lower models respectively. The simulation results in Hexi region of Gansu province show that the proposed model can effectively improve the power of tie-lines.

With the large-scale wind power connected to the power grid, the volatility and uncertainty of wind power output will cause fluctuations in the power of the tie line between the interconnected regional power grids, resulting in the limit of the power of the tie line, affecting the assessment of the power system and even threatening system security. Therefore, this paper proposes an evaluation index prediction method of tie line power control based on LSTM. Use historical data of a grid tie line as input, and establish a prediction model and predict the tie line power in advance. The CPS standard for the tie line control performance evaluation index is introduced, and the CPS indicator is predicted based on the tie line power prediction. The results of the example show that the power of the tie line predicted by LSTM is basically the same as the actual power, and the CPS indicator is more reliable. Comparing the prediction method with the results of other prediction methods, the error is small, and the feasibility and effectiveness of the above prediction method for the evaluation of tie line control performance are verified.

Flexible adjustments of the high voltage direct current (HVDC) tie-line transmission power can promote the cross-region consumption of wind power and relieve the peak regulating pressure of the thermal units in sending end grid. However, the reactive power control equipment (RPCE) acts frequently while the HVDC tie-line transmission power changes, which will reduce the service life of RPCE and is not conducive to the safe operation of power grid. An optimal method of HVDC tie-line scheduling considering RPCE action times is proposed in this paper. Firstly, an operation model of security constrained HVDC tie-line scheduling is established based on the generalized Benders decomposition (GBD) method; secondly, the link constraints of RPCE are established both in master problem and sub-problems inspired by the idea of alternating iteration, which realize the discretization and unification of RPCE; thirdly, the constraints of RPCE action times are added to the master problem, which limit the action times of RPCE. A case study is carried out based on a two-area 48-bus system, verifying the validity and accuracy of the method.

Change in frequency with load is a great concern. In this paper a load frequency problem is address by taking two area power systems with hydro and wind power plant in each unit in the first instant. Then SMES and HVDC link is introduce in the system to improve the system performance. In all the cases TID controller is used and the parameters of controller, SMES and HVDC link are tuned using Differential Evolution (DE) algorithm. The whole system is design in MATLAB/SIMULINK model; different load pattern is applied in place of step load and results show that with SMES and HVDC link the improvement of system occurs in terms of deviation of frequency and tie line power.

Change in frequency with load is a great concern. In this paper a load frequency problem is address by taking two area power systems with hydro and wind power plant in each unit with PID/PI-PD. Then RFB and UPFC are introduced in the system to improve the system performance. In all the cases PID/PI-PD controller is used and the parameters of controller, RFB and UPFC are tuned using Differential Evolution (DE) algorithm. The whole system is design in MATLAB/SIMULINK model; different load pattern is applied in place of step load and pulse load results show that with PI-PD controller the improvement of system occurs in terms of deviation of frequency and tie line power.

The large-scale inverter interfaced generators (IIG) integrated into power system shows more and more unique fault features. There are adaptability issues when traditional distance protections are used in such system. Aiming at the adaptability problem of distance protection configured on the tie line, a simulation model is built according to the local grid and the distance protection algorithm in protection device, and the influence of IIG on the distance protection of different principles in the actual protection device is comprehensively analyzed. The research results show that, due to the fault characteristics of IIG, the IIG side distance protection is prone to refuse to operate and misoperation, and the system side distance protection is prone to reverse misoperation. The research results of this paper provide reference for the engineering application and performance improvement of distance protection.