Power Transmission Limits Research Articles

The Power-Transmission Limit of the Controlled High-Voltage Transmission Line for Modes at the Static Stability Boundary

The Power-Transmission Limit of the Controlled High-Voltage Transmission Line for Modes at the Static Stability Boundary

Comparative Study of the Transmission Capacity of Grid-Forming Converters and Grid-Following Converters

The development trend of high shares of renewables and power electronics has increased the demand for new energy converters in the power system, but there is a lack of systematic research on the stability of different types of converters when transmitting power, which is worth exploring in depth. In this study, the power transfer capabilities of grid-forming and grid-following converters are investigated separately through an equivalent circuit diagram and phasor diagram when connected to the grid, and a quantitative relationship between converters’ power transmission limit and short circuit ratio under static stability conditions is obtained, leading to the conclusion that, in terms of power transmission, grid-forming converters are more suitable for weak grids with high damping and low inertia, whereas grid-following converters are more suitable for strong grids with high inertia. The conclusions are further verified by constructing the converter grid-connected models for different grid strengths through the PLECS simulation platform and the real-time simulation RTBOX1 and F28379D launchpad platform.

Optimal Energy Forecasting Using Hybrid Recurrent Neural Networks

The nation deserves to learn what India’s future energy demand will be in order to plan and implement an energy policy. This energy demand will have to be fulfilled by an adequate mix of existing energy sources, considering the constraints imposed by future economic and social changes in the direction of a more sustainable world. Forecasting energy demand, on the other hand, is a tricky task because it is influenced by numerous micro-variables. As a result, an macro model with only a few factors that may be predicted globally, rather than a detailed analysis for each of these variables, is required. In this work, a hybrid approach is proposed for identifying the optimal generation-based mix of electricity systems in India. This approach is developed by combing Recalling-Enhanced Recurrent Neural Network (RERNN) and Giza Pyramids Construction (GPC). RERNN possesses selective memory features whereas GPC is a meta-heuristic algorithm that deals with different sets of problems. The goal of this approach is to assess the present load requirements and production profile to understand the current requirement and its production methods. Data on regards to electricity load profile involving the generation of all power plants, capacity factors and transmission limits were gathered from different sources including the Indian National Load Dispatch Centre, Central Electricity Authority database, annual reports of India and regional load dispatching centers. The proposal has introduced the RERNN technique to analyze the optimal time series whereas the GPC technique is involved in the optimization of RERNN parameters. The present work is simulated in MATLAB and the performance assessed with different parameters. The present technique gives an effective results in terms of accuracy, computational efficiency and feasibility.

Analysis of Power Transmission Limit of Grid-Connected Inverters Based on the Impedance Method

Analysis of Power Transmission Limit of Grid-Connected Inverters Based on the Impedance Method

A Method for Analyzing the Voltage Deviation Isolation Performance With an Application in Two-Stage High-Frequency Isolated AC-DC Converters in LVDC Systems

The differences between the power quality at the AC and DC sides, caused by AC-DC converters with constant DC voltage control, commonly exist in low-voltage direct current (LVDC) systems. The voltage deviation isolation (VDI) is one of the typical phenomenons. A method is proposed to analyze the VDI performance and applied in two-stage high-frequency isolated AC-DC converters, which can isolate not only the faults but also the voltage deviation at the AC side and improve the voltage quality at the DC side. First, the voltage deviation isolation ratio (VDIR) is defined to assess VDI. Based on VDIR, the operation characteristics of AC-DC converters with constant DC voltage control are analyzed and the range of VDI is defined. Second, with considering the conditions for stable operation of AC-DC converters, constraints on power transmission limit and static stability limit are used to determine the range of VDI. Third, a simulation model is established and the feasibility and validity of the method are verified. Finally, the main factors affecting the range of VDI are analyzed. Actually, the method proposed is adapted to various types of AC-DC converters with constant DC voltage control.

Steady-state voltage-control method considering large-scale wind-power transmission using half-wavelength transmission lines

Half-wavelength transmission can transmit large-scale renewable energy over very long distances. This paper proposes an improved steady-state voltage-control method for half-wavelength transmission systems considering large- scale wind-power transmission. First, the unique voltage characteristics of half-wavelength lines are deduced based on the distributed parameter model. In the secondary voltage-control level, reactive power-transmission limits of half-wavelength lines are introduced as another control objective except for tracing the pilot bus voltage reference. Considering the uncertainty and fluctuation of wind power, the overvoltage risk-assessment method of half-wavelength lines is presented to determine specific voltage-control strategies. Simulation results demonstrate that the proposed voltage-control method delivers superior tracking performance according to a voltage reference value and prevents the overvoltage risk of half- wavelength lines effectively in different wind-power penetrations.

Comparative Study of Different Antenna Configurations for the MIMOOSTBC Technique Using FEC and the Rayleigh Fading Channel

Background: Multi-Input Multi-Output (MIMO) systems using Orthogonal Space-Time Block Coding (OSTBC) gained extensive popularity in wireless applications owing to the potential of providing improved reliability. Methods: The performance of MIMO - OSTBC systems using error-correcting code (Convolutional, Reed Solomon and Interleaving) schemes used to encode data streams in wireless communications using the Rayleigh channel is reported here. These are subjected to experimentation under modulation schemes such as Quadrature Phase Shift Keying (QPSK). Decoding occurs using the Maximum Likelihood (ML) algorithm, which provides high data rates using spatial domains under the limits of power transmission and limited bandwidths. Results: Different simulations are performed to detect the best BER performance for various antenna configurations and values of antenna configurations with Error Correction so as to use the best outcomes to model the OSTBC. Conclusion: Their effect of improving the overall can be noticed by the advantages of OSTBC with the correcting codes and the maximum number of configurations.

Calculating the Interface Flow Limits for the Expanded Use of High-Voltage Direct Current in Power Systems

Although loads are increasingly becoming concentrated in metropolitan areas, power generation has decreased in metropolitan areas and increased in nonmetropolitan areas; hence, power transmission must occur through interface lines. To achieve this, additional transmission lines must be secured because the existing interface lines have reached their large-scale power transmission limits. The Korea Electric Power Corporation has installed many high-voltage direct current lines, thereby impacting the determination of interface power flow limits. These serve as the basis for system operations. However, knowledge of operating high-voltage direct current lines as a simple transmission line in a single power system is lacking. The effects of high-voltage direct current and its related parameters for interface flow limit analysis remain unclear. Furthermore, whether high-voltage direct current should be included in the selection of the interface lines that serve as the basis for interface flow remains unclear. In addition, whether the high-voltage direct current line faults should be included in the contingency list for determining the interface flow limits has not been considered. Additionally, it has not been determined whether to operate the DC tap when performing the simulation This study addresses these issues and determines the conditions that are necessary for determining the interface flow limits when a high-voltage direct current transmission facility has been installed in a land power system. The results conclude how to reflect the above conditions reasonably when performing the interface flow limit analysis on a system that includes the HVDC lines.

A short-term decision-making model for a price-maker distribution company in wholesale and retail electricity markets considering demand response and real-time pricing

Adopting strategic behavior in the wholesale electricity market can revolutionize the performance of the Distribution Company (DisCo) in the operation of the distribution network. Besides, the demand response program in real-time pricing (RTP) environment, which is practicable within the smart distribution network, has a significant positive impact on the strategic behavior of this company. In this paper, a new framework is proposed to develop the sell and purchase strategies for a strategic distribution company in the energy and retail markets. The DisCo in this paper is the owner and operator of the distribution system that can affect the price of the energy due to the ownership of conventional and energy storage systems (ESSs). The uncertainty associated with the demands within the distribution network is considered by sets of scenarios. Also, the elasticity of the demands, which pertains to the retail price, is taken into account in the demand response program. Retail energy prices are also determined for customers under the RTP scheme. The problem is modeled in the form of a bi-level optimization problem, the upper-level of which includes maximizing the profit from energy sales to consumers under the RTP scheme and managing the production of distributed generation (DG) units, amount of charging or discharging of the storage system and deciding about LC program. And the lower-level is a market-clearing of the wholesale market aiming at maximizing social welfare. The upper network (sub-transmission network) is modeled in the form of a DC load flow equations to consider the impact of power transmission limits. By converting the bi-level problem to MPEC model and linearizing it using the dual theory and KKT conditions to a MILP model, finally, the MILP model is solved using the GAMS software. The performance of the proposed model is shown in two case studies, based on the IEEE-33BUS distribution network, and the 3-bus and 14-bus sub-transmission networks. Simulations investigate the impact of the strategic behavior of the DisCo on the financial and technical aspects of its operations. Simulations also indicate that the proposed model is an appropriate tool for analyzing the performance of the strategic DisCo in the wholesale and retail energy markets. Also, using the proposed approach can result in increasing of DisCo’s profit, while declining in wholesale prices and load interruptions.

An Efficient Upgradation of STATCOM to PV-STATCOM and Result Estimation using SIMULINK

Power generation is a much discussed topic in research works recently. Power production from different renewable source were the most processed topic. There are large number of solar farms which produce heavy electricity throughout the world but the overall efficiency of those solar farms remain unutilized especially in morning and evening when the sunlight is at its minimum the power production is too low. The series of Photovoltaic Cells (PV) are responsible for power production which are connected with the grid. The solar power output is D.C which can be transformed into A.C by inverter injection in the production line. STATCOM is proposed system which is a device is coming from the sub categorization of FACTS. STATCOM is concentrated on voltage source transformer. It operates in accordance as rectifier and inverter is used to increase power transmission limits. It also has the feature of damping control. The overall gist of the system is we propose a PV-STATCOM control concept. We use MATLAB 2013a to develop a Simulink simulation of PV-STATCOM system. It will be a solar inverter which is voltage controlled and it has overall inverter properties too.

Advanced Drone Battery Charging System

In this work, an advanced drone battery charging system is developed. The system is composed of a drone charging station with multiple power transmitters and a receiver to charge the battery of a drone. Resonance inductive coupling-based wireless power transmission technique is used. With limits of wireless power transmission in inductive coupling, it is necessary that the coupling between a transmitter and receiver must be strong for efficient power transmission but for a drone, it is normally hard to land it properly on a charging station or a charging device to get maximum coupling for efficient wireless power transmission. Normally some sensors are used to align the transmitter and receiver for proper coupling but in this system, a novel method based on Hill climbing algorithm is proposed to control the coupling between the transmitter and a receiver without using any sensor. The feasibility of the proposed algorithm is checked using MATLAB. A practical test bench is developed for the system and several experiments are conducted under different scenarios. The system is fully automatic and works well to eliminate the poor landing and coupling effect which hinders the efficient wireless power transmission.

Research on Power Transmission Capability of VSC-HVDC Based on Second Order LADRC

Voltage source converter based high voltage direct current (VSC-HVDC) technology is considered one of the most desirable technique for massive renewable power integration, for which converter controller design and power transmission capacity research are two essential topic. A novel VSC-HVDC converter station controller is proposed based on second order linear active disturbance rejection control (LADRC), which realizes rapid and independent adjustment of active and reactive power. The controller take full advantage of ADRC to improve dynamic response and to strengthen robustness as well as disturbance rejection ability of the system. A small signal model of overall system including AC system dynamics is established. Based on eigenvalue analysis, power transmission limit of VSC-VHDC is investigated on the perspective of global stability of the whole system. The influence of control strategy and reactive control mode on VSC power transmission capacity are then analyzed respectively. Examples are given to verify the results obtained by small signal stability analysis. The research in the paper provides theoretical support for the application of LADRC in VSC-HVDC domain.

Analysis of power transmission limit for the VSC‐HVDC feeding weak grid

Analysis of power transmission limit for the VSC‐HVDC feeding weak grid

Optimization Model for the Short-Term Operation of Hydropower Plants Transmitting Power to Multiple Power Grids via HVDC Transmission Lines

Long-distance and large-capacity hydropower transmission from large hydropower plants in southwestern China to load centers is an important and effective measure for the accommodation of large-scale hydropower in China. However, the load demands of the receiving-end power grids are not fully considered in the conventional power transmission mode, which has greatly affected their enthusiasm for the absorption of trans-regional hydro energy. In order to make full use of the peak shaving capability of the hydropower plants, this paper develops an optimization model for determining the hourly generation scheduling of the hydropower plants transmitting electric power to several power grids via high voltage direct current (HVDC) transmission lines. A large-capacity and highly complex multi-unit hydropower system, the Xiluodu plant in China, is taken as the case study. In the proposed model, minimizing the peak-valley differences of multiple receiving-end power grids is adopted as the objective to alleviate the peak shaving pressure of the receiving-end power grids. In addition to the traditional hydraulic constraints, the operation constraints of individual units and HVDC power transmission limits are well considered. The study focuses mainly on modeling the stair-like power transmission curve constraint which is discrete and nonlinear and has been rarely considered in previous studies. This constraint is then linearized through limiting the logical relations between multiple binary integer variables. Case studies demonstrate that the proposed model has high computational efficiency, and the peak-valley differences of the two receiving-end power grids, i.e., Zhejiang Power Grid and Guangdong Power Grid, are decreased by 15.2% and 7.33%, respectively. Moreover, frequent conversion of HVDC converter equipment can also be avoided, which makes the obtained generation schedule more executable.

Practical limits of power transmission through single-mode chalcogenide fibers

Beam confinement or “no free-space optics” via fiber transmission can achieve improved reliability, lower cost, and reduced component count for active sensing systems. For midinfrared delivery, mechanically robust chalcogenide (arsenic sulfide) single-mode fibers are of interest. A 12-μm core diameter fiber is shown to transport >10 W at 2053 nm, and a 25-μm core diameter fiber enables single-mode beam transport from a 4550-nm quantum cascade laser. As midinfrared sources continue to increase their output power capabilities, chalcogenide fibers will eventually be limited in their power-handling capacity due to optical nonlinearities or thermal failure. These limitations are discussed and analyzed in the context of single-mode chalcogenide fibers in order to provide a framework for power transmission limitations in various operating regimes.

Development of Intelligent Drone Battery Charging System Based on Wireless Power Transmission Using Hill Climbing Algorithm

In this work, an advanced drone battery charging system is developed. The system is composed of a drone charging station with multiple power transmitters and a receiver to charge the battery of a drone. A resonance inductive coupling-based wireless power transmission technique is used. With limits of wireless power transmission in inductive coupling, it is necessary that the coupling between a transmitter and receiver be strong for efficient power transmission; however, for a drone, it is normally hard to land it properly on a charging station or a charging device to get maximum coupling for efficient wireless power transmission. Normally, some physical sensors such as ultrasonic sensors and infrared sensors are used to align the transmitter and receiver for proper coupling and wireless power transmission; however, in this system, a novel method based on the hill climbing algorithm is proposed to control the coupling between the transmitter and a receiver without using any physical sensor. The feasibility of the proposed algorithm was checked using MATLAB. A practical test bench was developed for the system and several experiments were conducted under different scenarios. The system is fully automatic and gives 98.8% accuracy (achieved under different test scenarios) for mitigating the poor landing effect. Also, the efficiency η of 85% is achieved for wireless power transmission. The test results show that the proposed drone battery charging system is efficient enough to mitigate the coupling effect caused by the poor landing of the drone, with the possibility to land freely on the charging station without the worry of power transmission loss.

A Methodology for Determining Permissible Operating Region of Power Systems According to Conditions of Static Stability Limit

For power systems with long-distance ultra-high-voltage (UHV) transmission lines, power transmission limits are often determined by static stability limits. Therefore, the assessment of stability and finding solutions to improve the stability reserve are essential for the operation of the system. This article presents an analytical approach to construct limit characteristics according to static stability conditions on a power plane. Based on the approach proposed, a program is developed and tested on a system with long-distance UHV transmission lines, showing a good performance.

An Improved Phase-Locked-Loop Control with Alternative Damping Factors for VSC Connected to Weak AC System

The gains of phase-locked-loop (PLL) have significant impacts on the power transfer limits for the voltage source converter (VSC) connected to weak AC system. Therefore, in this paper, an improved PLL control, respectively, with alternative damping factors for rectifier and inverter is proposed. First, it is proved that the impedance angle of AC system has a great impact on the small-signal stability of the VSC system. With the same variation tendency of Thévenin equivalent resistance, the limits of power transmission are changing in opposite trends for rectifier and inverter. Second, the improved PLL with alternative damping factors is proposed based on the participation factor analysis. Third, the optimal damping factors of the improved PLL control for rectifier and inverter are calculated. Simulations and calculations validated the following three conclusions: (1) in rectifying operation, the equivalent system resistance has a negative impact on the stability of the system and this is not the case for inverting operation; (2) adding the alternative damping factors to PLL control shows similar results compared with changing the impedance angle of AC system; (3) the proposed optimal damping factors of PLL can effectively extend the power transfer limits under both rectifier and inverter modes.

Interdependency Assessment of Coupled Natural Gas and Power Systems in Energy Market

AbstractOwing to the technological development of natural gas exploration and the increasing penetration of gas-fired power generation, gas and power systems inevitably interact with each other from both physical and economic points of view. In order to effectively assess the two systems’ interdependency, this paper proposes a systematic modeling framework and constructs simulation platforms for coupled gas and power systems in an energy market environment. By applying the proposed approach to the Australian national electricity market (NEM) and gas market, the impacts of six types of market and system factors are quantitatively analyzed, including power transmission limits, gas pipeline contingencies, gas pipeline flow constraints, carbon emission constraints, power load variations, and non-electric gas load variations. The important interdependency and infrastructure weakness for the two systems are well studied and identified. Our work provides a quantitative basis for grid operators and policy makers to support and guide operation and investment decisions for electric power and natural gas industries.

New Control of PV Solar Farm as STATCOM (PV-STATCOM) for Increasing Grid Power Transmission Limits During Night and Day

This paper presents a novel concept of utilizing a photovoltaic (PV) solar farm inverter as STATCOM, called PV-STATCOM, for improving stable power transfer limits of the interconnected transmission system. The entire inverter rating of the PV solar farm, which remains dormant during nighttime, is utilized with voltage and damping controls to enhance stable power transmission limits. During daytime, the inverter capacity left after real power production is used to accomplish the aforementioned objective. Transient stability studies are conducted on a realistic single machine infinite bus power system having a midpoint located PV-STATCOM using EMTDC/PSCAD simulation software. The PV-STATCOM improves the stable transmission limits substantially in the night and in the day even while generating large amounts of real power. Power transfer increases are also demonstrated in the same power system for: 1) two solar farms operating as PV-STATCOMs and 2) a solar farm as PV-STATCOM and an inverter-based wind farm with similar STATCOM controls. This novel utilization of a PV solar farm asset can thus improve power transmission limits which would have otherwise required expensive additional equipment, such as series/shunt capacitors or separate flexible ac transmission system controllers.