Stability Of Power Transmission Research Articles

System for wireless power transfer to rotating objects with stable power transmission based on parity-time symmetry

System for wireless power transfer to rotating objects with stable power transmission based on parity-time symmetry

Analysis on Transmission Characteristics of Dynamic Magnetic Coupling Mechanism of Racetrack Coil with Deflection Angles

In dynamic magnetically coupled contactless power transmission, the fluctuation of mutual inductance is caused by the relative motion between transmission and receiving coils, which affects the stability of power transmission. In order to reduce the fluctuation characteristics of power transmission, the mutual inductance calculation model of transmission mechanism including a racetrack coil with deflection angle is established by using Neumann formula, and the influence of different deflection angle and layout on mutual inductance fluctuation characteristics is analyse and compare. Then the power transmission system with LCC-S compensation for the transmission mechanism is established. The transmission characteristics of the racetrack coil with deflection angle are studied. The results show that reasonable design of the deflection angle can reduce the fluctuation of the mutual inductance and the power output in dynamic transmission. The fluctuation of power output can also be reduced by changing the distance between transmission coils and the length of straight side of receiving coils.

Enhancing Power Transmission Stability with HVDC Systems During Load Contingencies

Enhancing Power Transmission Stability with HVDC Systems During Load Contingencies

Regional Sensitivity Analysis for Maximum Static Transfer Capability of Power Systems by Dimension-Adaptive Sparse Grid Interpolation

The maximum static transfer capability (MSTC) can be regarded as a measure of the power transmission ability of power systems in steady-state operation. These emerging uncertainty sources pose a difficult challenge for the efficient analysis and effective control of MSTC. To address this challenge, the dimension-adaptive sparse grid interpolation (DASGI) method is applied with modified boundaries of the collocation points to establish a surrogate model for the faster calculation of the MSTC based on AC optimal power flow (AC-OPF), thus accelerating its probabilistic analysis as well. Subsequently, the regional sensitivity analysis (RSA) is introduced in terms of contribution to the sample mean (CSM) and to the sample variance (CSV) to identify the critical regions of the uncertainty sources. Hence, an adjustment strategy is developed to increase the mean or decrease the variance of MSTC for secure and stable power transmission. Furthermore, the total CSM (TCSM) and total CSV (TCSV) are proposed as indicators to select the most influential random inputs as the preliminary step of RSA, which reduces the analytical burden. The effectiveness of this proposition is illustrated on the modified IEEE 118-bus system and the Polish 2383-bus power system, where the Monte Carlo simulation method, in combination with the AC-OPF-based MSTC model, provides an accuracy reference and a traditional sensitivity index provides the term for comparison.

Multi-Defect Detection Network for High-Voltage Insulators Based on Adaptive Multi-Attention Fusion

Insulators find extensive use across diverse facets of power systems, playing a pivotal role in ensuring the security and stability of electrical transmission. Detecting insulators is a fundamental measure to secure the safety and stability of power transmission, with precise insulator positioning being a prerequisite for successful detection. To overcome challenges such as intricate insulator backgrounds, small defect scales, and notable differences in target scales that reduce detection accuracy, we propose the AC-YOLO insulator multi-defect detection network based on adaptive attention fusion. To elaborate, we introduce an adaptive weight distribution multi-head self-attention module designed to concentrate on intricacies in the features, effectively discerning between insulators and various defects. Additionally, an adaptive memory fusion detection head is incorporated to amalgamate multi-scale target features, augmenting the network’s capability to extract insulator defect characteristics. Furthermore, a CBAM attention mechanism is integrated into the backbone network to enhance the detection performance for smaller target defects. Lastly, improvements to the loss function expedite model convergence. This study involved training and evaluation using publicly available datasets for insulator defects. The experimental results reveal that the AC-YOLO model achieves a notable 5.1% enhancement in detection accuracy compared to the baseline. This approach significantly boosts detection precision, diminishes false positive rates, and fulfills real-time insulator localization requirements in power system inspections.

A Detuned S-S Compensated IPT System With Two Discrete Frequencies for Maintaining Stable Power Transfer Versus Wide Coupling Variation

Stable power transmission is one of the key factors in the inductive power transfer (IPT) system. However, misalignment between the primary and secondary sides is almost inevitable in practice, affecting the system performance due to the coupling variation. With the widespread use of IPT technology, it is desired to transfer power from the primary side to the secondary side with a wide misalignment range as large as possible. To address this issue, the design method of the detuned circuit is widely applied in the IPT system. This paper analyzes the characteristics of the transfer power of the detuned series–series (S-S) topology with frequency variations and proposes a maintaining stable power transfer method versus wide coupling variation by adopting two discrete frequencies. Further, a design step is given to obtain the system parameters. Theoretical and experimental results are provided to demonstrate the misalignment performance of the proposed method. The results show that the coupling range is extended from [0.115-0.2] to [0.115-0.27] with the 5.6% fluctuation of the output power, and the corresponding efficiency varies from 91.46% to 95.52%.

VSC-HVDC control without PLL for unbalanced grid

When unbalanced faults such as single-phase voltage drop occur in the power grid, VSC-HVDC will fail or become unstable due to sudden changes in amplitude, phase, frequency, etc. of the power grid voltage. Therefore, the role of PLL in a non-ideal power grid is particularly important, but often PLL needs to make a compromise between dynamic response and system stability. Therefore, this paper proposes a free-PLL control strategy under non ideal power grid. First, according to the power transmission model of VSC-HVDC under power grid imbalance, the control command required by the inverter is given, which is determined in the environment free-PLL. Therefore, PLL is not required to retrace the phase of the grid voltage. In addition, in order to overcome the impact of the sudden change of power grid frequency on the free-PLL strategy, a frequency locking strategy is proposed in the free-PLL environment, the response time is about 1 grid cycle. Finally, in order to verify the effectiveness and correctness of the proposed strategy, the VSC-HVDC system’s active power transmission stability is guaranteed when the grid voltage encounters different degrees of single-phase sags.

Impacts of Trans-Provincial Thermal Power Transmission on Air-Quality Recovery and Related Health Outcomes in China.

Trans-provincial thermal power transmission has become an important measure for optimizing power allocation and alleviating the mismatch between regional power production and consumption in China, however, leading to inter-regional redistribution of air pollution. Here, we investigated the impacts of thermal power transmission on air-quality recovery and related health outcomes in China. The results showed that the redistribution of air pollutant emissions contributed to air-quality improvements and health benefits in the eastern regions but to the opposite side in the western regions. On a national scale, trans-provincial thermal power transmission contributed to a change in air quality from slightly polluted to good conditions for a period of 9 days under the standard of 75 μg m-3, accounting for 1.8% of the total number of polluted days in 4 months of 2017 and promoting air-quality recovery in China. Furthermore, the recovery totally reduced the number of premature deaths (exposed to fine particulate matter, PM2.5) by 2392 persons (95% confidence interval: 1495-3124) in 2017. Owing to thermal power retrofits and stable power transmission structure, transmission network expansion during the last decade has not brought significant changes in its impacts on air pollution. However, the environmental inequity caused by thermal power transmission stimulates further attention on coordinating regional interests in air pollution control through various production-side and consumption-side measures.

Research on an Insulator Defect Detection Method Based on Improved YOLOv5

Insulators are widely used in various aspects of the power system and play a crucial role in ensuring the safety and stability of power transmission. Insulator detection is an important measure to guarantee the safety and stability of the transmission system, and accurate localization of insulators is a prerequisite for detection. In this paper, we propose an improved method based on the YOLOv5s model to address the issues of slow localization speed and low accuracy in insulator detection in power systems. In our approach, we first re-cluster the insulator image samples using the k-means algorithm to obtain different sizes of anchor box parameters. Then, we add the non-local attention module (NAM) to the feature extraction module of the YOLOv5s algorithm. The NAM improves the attention mechanism using the weights’ contribution factors and scaling factors. Finally, we recursively replace the ordinary convolution module in the neck network of the YOLOv5 model with the gated normalized convolution (gnConv). Through these improvements, the feature extraction capability of the network is enhanced, and the detection performance of YOLOv5s is improved, resulting in increased accuracy and speed in insulator defect localization. In this paper, we conducted training and evaluation on a publicly available dataset of insulator defects. Experimental results show that the proposed improved YOLOv5s model achieves a 1% improvement in localization accuracy compared to YOLOv5. The proposed method balances accuracy and speed, meeting the requirements of online insulator localization in power system inspection.

Enhancing Power Transmission Stability of AUV’s Wireless Power Transfer System with Compact Planar Magnetic Coupler

In this paper, a wireless power transfer (WPT) system with a compact planar magnetic coupler for an autonomous underwater vehicle (AUV) is proposed. A passive induction (PI) coil is integrated into the circular transmitter (Tx) coil to build a uniform magnetic field (UMF), which can guarantee the stable output of the WPT system under uncertain radial and axial misalignments for AUV. Based on normalized magnetic induction intensity distribution analysis, a UMF constructing method with a PI coil is given, aiming to eliminate the fluctuation of magnetic field intensity, and the PI coil design principles and flow chart are obtained. The theoretical analysis shows the proposed integrated coil can effectively enhance the radial misalignment tolerance compared with a conventional circular spiral coil. The zero-phase angle (ZPA) input condition can be achieved by adjusting the series capacitor connected with the Tx coil in S-S compensation topology. Experimental results show that the proposed magnetic coupler containing an integrated coil significantly improves the stability of output power and power transfer efficiency within the possible radial and axial misalignments compared with a conventional coupler. It was demonstrated that the output power changes less than 5.5% and the power transfer efficiency maintains at approximately 84.5% in arbitrary radial positions within the possible working region with an axial transfer distance of 50 mm in saltwater.

PT Symmetry-Based AUV Dual Transmission Coil Wireless Power Transfer System Design

Autonomous underwater vehicles (AUVs) are widely used for ocean exploration; however, the way they are replenished becomes the biggest issue limiting their range and efficiency. A dual transmission coil wireless power transfer (DTCWPT) system based on parity–time (PT) symmetry is proposed in this paper to realize an autoadaptive constant power transmission. A shielded housing structure for coils is equipped to realize WPT in the ocean. In the offset experiments, the proposed dual transmitting coil structure was able to achieve a stable power transmission of 39 W within an offset range of 8.1 cm. It is obvious that the DTCWPT system based on PT symmetry could charge an AUV in the ocean with high robustness. This paper provides a novel solution based on DTCWPT for AUV energy supply. The proposed DTCWPT system could offer remarkable improvements in the navigation performance of AUVs.

Transmission range extension strategy of parity–time‐symmetry‐based wireless power transfer system by a boost converter

AbstractThe wireless power transfer (WPT) system based on the parity–time (PT) symmetry can realize stable power transmission with constant efficiency and output power in the PT‐symmetric region. In some applications with long transmission distance requirements, such as medical treatment, it is meaningful to expand the PT‐symmetric region by reducing the critical coupling coefficient. Therefore, a novel WPT system based on PT symmetry with a boost converter in secondary side is proposed in this article to expand the transmission range. The circuit theory is used to analyze the presented system. Then two models with different drive signals of the boost converter are established and simulated respectively to show the effect of the proposed system compared with the original PT‐symmetry‐based WPT system. Finally, the experimental results verify that the proposed system can play a role in extending the stable transmission distance or in suppressing the output power growth of the PT‐symmetric‐based WPT system.

IASA-Based Capacity Allocation Optimization Study for a Hydro–Pumped Storage–Photovoltaic–Wind Complementary Clean Energy Base

Photovoltaic and wind power is uncontrollable, while a hydro–pumped storage–photovoltaic–wind complementary clean energy base can ensure stable power transmission in the whole system through power quantity regulation by the hydropower station and the pumped storage station. Reasonable allocation of installed capacities of various power sources in the system can improve the reliability and economy of systematic power supply. A system model was built generalizing the hydropower station and the pumped storage station as an energy storage unit, compensating and regulating the natural output process to match the system output and the load and to establish a correlation between the installed capacity of the base and the output index. Installed capacity allocation optimization was studied through an optimization model built with an initial investment of the base as the objective function and with power supply guarantee rate, power abandonment rate, and installed capacity as restraints and solved using improved artificial sheep algorithm (IASA) based on the shepherd dog supervision mechanism. A Yellow River clean energy base was selected for a case study analyzing the influence of power supply guarantee rate and power abandonment rate on installed capacity allocation and investment. For the two most important parameters in the optimization process, that is, the power supply guarantee rate and the power abandonment rate, after qualitative and quantitative analysis, it is found that the power supply guarantee rate has a greater impact on the initial investment. In this study, a combination of the power abandonment rate of 18% and the guaranteed rate of 90% is finally selected for the optimization calculation. The case study indicates that sole increase of installed photovoltaic or wind capacity resulted in the increase of both power supply guarantee rate and power abandonment rate; an appropriate increase in the installed capacity of the pumped storage station raised the power supply guarantee rate and lowered the power abandonment rate; and the optimal installed capacity allocation of the photovoltaic, wind, pumped storage, and hydropower under a specific load condition of the case project is 4.6:1.4:1.7:1.

A Robust Parity-Time-Symmetric WPT System With Extended Constant-Power Range for Cordless Kitchen Appliances

Cordless kitchen appliances powered by wireless power transfer (WPT) technology can operate without the clutter of cords, making them safer and easier to clean. In order to allow cordless kitchen appliances to be placed more freely, this article proposed a parity-time (PT) symmetric WPT system with stable output power in the whole coupling range. Here, a new implementation of a PT-symmetric circuit using a combination of self-oscillating methods and pulsewidth modulation (SO-PWM) is presented. The self-oscillating mode is activated in the strong coupling region, which guarantees a constant output power and constant transfer efficiency against the coupling coefficient variation. In the weak coupling region, the PWM mode with a fixed frequency and a variable duty cycle is adopted, and a control strategy based on primary-side-only parameters is presented to obtain stable power transmission. Besides, a corresponding coupling-region detection method based on the reflected resistance is proposed to ensure smooth switching between SO mode and PWM mode. The advantage is that the stable output power can be maintained in the whole coupling region without any extra dc–dc converter and dual-side communication requirements, while maintaining the same transfer efficiency as the standard PT-symmetric WPT system. A 500-W experimental prototype is built to verify the theoretical analysis. The results show that with a transfer efficiency of over 91.6%, the misalignment tolerance can be increased by 172%.

제안한 Half Bridge Sub-module을 통한 Modular Multilevel HVDC 시스템의 DC 고장 사고에 대한 차단

In power transmission of multi-system systems based on renewable energy today, high voltage DC transmission based on modular multi-level converter has many advantages in terms of high power quality and cost. Here, protection against external factors such as faults and rapid system recovery are very important issues for stable power transmission. In this paper, a method for system protection from the line to line DC faults on the grid is poposed. The proposed method is a method of suppressing the fault current by forming an inverse voltage slope through the fault ride through (FRT) method in the AC link and converter system according to a command operated in the event of a fault in the path of the fault current formed. The proposed method can be composed of semiconductor devices that are reduced compared to the existing sub-module models. For the verification of the paper, simulation through PSIM was used.

A novel hybrid propulsion system configuration and power distribution strategy for light electric aircraft

Similar to the electrification of the automotive industry, the growing concerns with the shortage of fossil fuels has also called for a paradigm shift in aviation industry. To promote the aviation electrification process, it is necessary to develop an efficient energy storage system and a stable power transmission system to improve the reliability and extend the endurance of electric aircraft. This paper designs a novel propulsion system topology and power distribution algorithm for light manned electric aircraft. Firstly, a novel aircraft hybrid propulsion system topology is designed, in which the battery energy storage system can work synergistically with the fuel cell to provide power to the aircraft electric engine. Then, an adaptive energy management framework is developed to distribute the aircraft power requirement between energy storage devices. Meanwhile, an aircraft power balance state recognizer is designed to enhance the dynamic performance of the aircraft and adjust the working state of the propulsion system. The proposed hybrid propulsion system configuration and power distribution algorithm are verified under a prototype two-seater electric aircraft: Alpha Electro. Numerical analysis results indicate that the developed methods can dynamically meet the power requirement of aircraft under fast-charging and peak power requirement scenarios. With the developed hybrid propulsion system, most of the fuel cell high-power working points are moved to the medium and low area, which indicates that the fuel cell is effectively protected. Furthermore, the quantified hydrogen consumption can be reduced by 7.63% comparing to fuel cell electric aircraft.

Improving the Voltage Quality and Power Transfer Capability of Transmission System Using FACTS Controller

One of the main challenges of the future in the utility sector is constructing the new transmission line corridor. This is due to the fact that land compensation cost associated with the expansion of a new transmission line corridor becomes very expensive and also power transmission efficency is very low. In addition to that, the high carbon emission, which is the major challenge of the world right now, related to the additional conventional energy-based power generation to meet dramatically increased electricity demand and the volatility nature of the existing transmission networks are some of the main drivers to implement FACTS controller in transmission network for flexible, reliable, efficient and stable power transmission. This study accounts modeling of static VAR compensator (SVC), static synchronous compensator (STATCOM), unified power flow controller (UPFC) in a 5-bus transmission system to enhance transmission efficency and the quality of power supplied to the costomer. FACTS devices for improving the transmission line capacity and voltage profile of the power system. The three FACTS controllers are modeled for the standard 5 bus IEEE system based on Newton Raphson algorithm using NEPLAN simulation software in order to investigate their impacts on transmission line capacity and voltage profile improvement. Based on the simulation result, the voltage profile as well as the capacity of the IEEE 5 bus system is improved well by using each of the FACTS controller. From the simulation result we can conclude that the STATCOM and SVC are very efficent in voltge profile improvement whereas the UPFC is well performed for the power transmission capability of the transmission network.

An Improvement of SNR for Simultaneously Wireless Power and Data Transfer System with Full-Duplex Communication Mode

The power interference is always inevitable in the simultaneous wireless power and data transfer (SWPDT) system resulting in the lower signal to noise rate (SNR) and may cause the failure of communication. Besides, the interference between bidirectional data source is also the problem during the full-duplex communication. To solve these problems, in this article, an improvement of SNR for SWPDT system with full-duplex communication mode is proposed. In the power transfer channel, the double-sided LCCL compensation topology is selected due to its good performance of blocking the power interference on data transmission. Besides, the constant current characteristic of primary coil could guarantee the stability of power transmission. In the data transfer channel, a novel data transmission based on the dual-resonant structure is proposed to suppress the ipsilateral interference, and the full-duplex communication is achieved by two different frequencies. An optimization method of power and data transfer channel to improve SNR further is proposed after the analysis on interferences of power transmission and ipsilateral data source. Finally, the feasibility of proposed topology and the correctness of the parameter design method are verified by the simulation and experimental results.

Design of Climbing Robot for Power Transmission Tower Maintenance

Periodic maintenance of transmission lines is a necessary guarantee for stable power transmission and avoiding serious power accidents. In order to reduce the safety risk of the first person climbing the transmission tower and the last person going down the tower when climbing the transmission tower manually, this paper develops an auxiliary climbing robot for the maintenance of transmission tower based on the bionic climbing principle. It includes the modular mechanical structure of the main body lifting, obstacle crossing telescopic, terminal clamping, and body jacking, as well as airborne motion control system and hierarchical control system of upper computer monitoring terminal. The comprehensive test results of indoor and outdoor simulated transmission tower environment show that the robot system can effectively complete the high-altitude climbing of power tower, and ensure the follow-up tasks of hanging, dismantling, and maintenance of safety anti-falling device.

Синтез системного стабилизатора с применением методов нечеткой логики и нейронной сети

Power systems are large non-linear systems that are often subject to low frequency electromechanical oscillations with a frequency of 0.5–2.5 Hz. Power system stabilizers (PSS) are commonly used as effective and economically efficient means to dampen electromechanical oscillations of generators and increase the stability of power systems. PSS can increase the power transmission stability limits by adding a stabilizing signal through the channels of the automatic excitation control system. The article presents the results of training a neural network based on which a fuzzy logic PSS is obtained for increasing the stability of electric power systems. The synchronous generator rotor speed deviation and acceleration were taken as input data for the fuzzy logic controller. These variables have a significant effect on damping the rotor's electromechanical oscillations. The characteristics of the power system equipped with the proposed fuzzy logic based PSS are compared with its characteristics with a PSS with non-optimized parameters and without a PSS.