Power Transmission Capability Research Articles

Power Quality Enhancement in High-Voltage Transmission Systems Using STATCOM by Type 1 and Type 2 Fuzzy Logic Controllers

The continuing growth of load demand leads to increased power system complexity and interconnections. During faults and abnormal operating conditions, conventional power systems change the load flow in transmission lines, which may cause voltage drops or swells, and other power quality issues. Voltage regulation is connected to reactive power compensation in system busbars, and fixed capacitor banks are usually used for this purpose, but they are not flexible and dynamic enough to meet the power quality requirements. With power electronics development, flexible alternative current transmission systems (FACTS) became a popular solution for power quality improvement and power transmission capability increment in power systems, and FACTS can be categorized into series and shunt systems. In this study, STATCOM was used to improve the voltage profile in part of Iraq’s high-voltage transmission system during abnormal operating conditions, such as sudden load addition and removal, which causes voltage dip and voltage swell. Type 1 fuzzy logic controller and type 2 fuzzy logic controller were used as the outer controller in the STATCOM; both controllers were able to regulate the voltage magnitude by reducing the voltage dip from 1.32 to 0.4%, voltage swell from 1.02 to 0.5%, and voltage THD at the connecting point did not exceed 3%, indicating that SATACOM with FLC improves the voltage profile under different operating conditions.

Knowledge-assisted differential evolution based non-contact voltage measurement for multiconductor systems in smart grid

Multiconductor systems, such as overhead lines and multicore cables, are widely used in smart grids for their reliable power transmission capabilities. However, measuring the voltage of individual conductors in these systems has been challenging despite their promising applications. This paper proposes a novel framework to address this issue by utilizing a low-cost electric field (EF) sensor array and a knowledge-assisted differential evolution algorithm. The framework involves designing an annular EF sensor array to capture EF information around the multiconductor systems while ensuring its anti-interference capabilities through grounding and balanced electrodes. Furthermore, an optimization problem is formulated to reflect the model accuracy, and a knowledge-assisted differential evolution algorithm is proposed to optimize the voltage values and conductor positions by leveraging knowledge about the conductor positions and EF distribution. The use of this knowledge is expected to generate promising initial solutions for accelerating the optimization process. The proposed framework is experimentally validated, and the results demonstrate the robustness and accuracy of the EF sensor array and algorithm in obtaining the voltage of individual conductors in multiconductor systems.

AC fault ride-through control strategy of MMC-UHVDC system with hierarchical connection mode

The ultra-high voltage direct current (UHVDC) transmission composed of modular multilevel converters (MMC) is an important technology for large-scale centralized transmission of renewable energy. In UHVDC system, temporary faults in the AC power grid system are a high probability fault, and the fault control strategy affects the safety and reliability of system operation. This paper studies on the condition of AC power grid faults occurring at the receiving converter station. Firstly, study the system characteristics after the occurrence of AC faults, and use theoretical analysis to derive the trend of DC voltage changes of each converter valve. Then, an AC fault ride-through control strategy with high power transmission capability is proposed with hierarchical connection structure, the strategy controls the system to synchronously reduce DC voltage and AC active power after a fault, maximizing the retention of the system’s transmission capacity during the occurrence of faults, thereby reduce power shock in the system. Finally, a simulation model of the dual ended system has built based on the PSCAD simulation platform. The simulation results show that when a single-phase ground fault and a three-phase ground fault occur in the high valve group at the receiving station, the system can retain about 83% and 50% of the transmission capacity during the fault period, respectively. Meanwhile, there is no serious overvoltage or overcurrent phenomenon in the system. The simulation results verified the effectiveness of the proposed control strategy.

Molecular dynamics simulation of arc ablation for CuCr contact materials and improvement method of ablation resistance

Renewable energy generation is a development trend worldwide due to sustainability and environmental protection. High-voltage direct current (HVDC) transmission is indispensable in the renewable energy system due to its efficient power transmission capability and adaptability to complex grid structures. The DC vacuum circuit breaker (VCB) is essential for system control and fault protection. However, with the development of DC systems towards high voltage and large current, the ablation resistance of CuCr contact materials in VCBs has become the leading technical bottleneck. In order to enhance the ablation resistance of CuCr contact materials, this paper investigates a new molecular dynamics (MD) simulation model for arc ablation of CuCr contacts; therefore, it proposes a design method for contact materials measured by characteristic parameters of ablation resistance. Results are as follows: Firstly, the Cu particles cause a severe ablation on CuCr contacts with the effect of arcs. Subsequently, the model’s accuracy is verified by the influence of Cr content on ablation resistance. Furthermore, Mo and W metal elements were used to dope and strengthen the CuCr10 contact material, and CuCr8Mo2 and CuCr7Mo3 have an apparent improvement in resistance to arc ablation, which are alternatives for reinforced CuCr10 contact materials.

An Investigation of Increased Power Transmission Capabilities of Elastic–Plastic-Designed Press–Fit Connections Using a Detachable Joining Device

An Investigation of Increased Power Transmission Capabilities of Elastic–Plastic-Designed Press–Fit Connections Using a Detachable Joining Device

Coordinated DC voltage control strategy for the receiving end hybrid LCC-VSC system

The receiving end hybrid line commutated converter (LCC) — voltage source converter (VSC) system has the obstacle that when an AC fault occurs at the sending LCC side, the DC voltage of the rectifier side will fall, resulting in the power transmission reduction of the whole system. Particularly, when the rectifier side DC voltage falls below the inverter side DC voltage, the power transmission is interrupted, posing a huge threat to the stability of the power grid at both the sending and receiving ends. To tackle these problems, a coordinated DC voltage control strategy for the receiving end is proposed. By controlling the DC voltage of the receiving VSC, the proposed method can improve the DC system power transmission capability when voltage drops at the sending side. The proposed control strategy is simple but practical, which is good for the stable and secure operation of both the sending and the receiving power system.

Analysis and Design of Independent DC Bus Structure Multiport Power Electronic Transformer Based on Maximum Power Transmission Capability of Low-Voltage DC Ports

Owing to the diverse connection configurations of dual active bridge converters, a multiplicity of low-voltage DC port structures are anticipated to emerge in the independent DC bus structure multiport power electronic transformer (IDBS-MPET). An inadequate low-voltage DC port structure exacerbates the power imbalance in IDBS-MPET, presenting a risk of overmodulation even when transmitting relatively low levels of power. To overcome this limitation, a design scheme of IDBS-MPET topology based on the maximum power transmission capability of the low-voltage DC ports is proposed in this paper. Three topology design rules are derived from the maximum power transmission capability results of more than 80 typical IDBS-MPET topologies. The symmetrical triple cross-phase connection structure, the symmetrical double cross-phase connection structure and the single-phase connection structure are sequentially identified as the three most optimal structures of low-voltage DC ports. By employing the proposed design methodology, each low-voltage DC port achieves its maximum power transfer capability relative to other configurations. The effectiveness of the proposed design scheme is validated by an optimal designed IDBS-MPET topology with six low-voltage DC ports.

Increasing the robustness of electrodynamic WPT systems with hybrid electromechanical transduction

In this paper, we compare the electrical damping capability of low-frequency electrodynamic wireless power transmission (EWPT) systems based on a resonant electromechanical receiver in the context of increasing their mechanical robustness. This study is carried out for piezoelectric (PE) and electrodynamic (ED) transducers. The receiver studied, excited by a distant transmitter coil, consists of a magnet and a resonant cantilever beam, and both ED and PE transducers (hybrid system). A strategy based on dual energy conversion is proposed that takes advantage of each transduction characteristic: the receiver with high-quality-factor is sufficiently sensitive to very weak excitation fields far from the transmitter, while it is robust to strong magnetic fields close to the transmitter by damping its motion. This approach is particularly relevant to increase the robustness of resonant receivers powering moving sensor nodes as the field strength seen by the receiver can vary greatly. This paper aims to evaluate three energy transduction strategies (PE-only, ED-only and hybrid) to both harvest more power and increase EWPT systems robustness by overdamping. An analytical model of the system is presented along with comparison with experimental results from a 71.7 cm3 prototype. When the motion amplitude is limited to 0.7 mm to limit aging, the receiver output 19 mW which outperforms the PE and ED modes alone by a factor of 1.5 and 1.8, respectively. Furthermore, the hybrid receiver can limit the amplitude of motion to 0.7 mm under a magnetic field up to 3.6 mT, which is 2.5 and 1.2 times higher than PE and ED alone, respectively.

Research on a novel water-cooling multi-cylinder magnetorheological transmission device.

Power transmission is an important application for magnetorheological (MR) fluid, and the cylinder-type power transmission device is a novel transmission form due to its high stability, higher transmission torque, and large ratio of power to mass. This work designed a novel multi-cylinder transmission device with a water-cooling channel because the MR transmission device, especially high-power MR transmission device, inevitably works in the high-temperature environment. Based on Ohm's law and electromagnetism theory, the magnetic circuit in the novel MR transmission device is designed, and the magnetoresistance was calculated. The finite element method is used to analyze the magnetic field in the device to ensure that the magnetic field in the working gap of MR fluid is strong enough for the MR effects. The temperature of the MR fluid inside the device is analyzed by the finite element method in the natural cooling state and the water-cooling state, respectively, so as to obtain the performance of water cooling. The novel MR transmission device is manufactured to verify its power transmission capability and heat-dissipation performance. The experimental results show that the novel device can transmit a maximum torque of 70 N m, consistent with the rated torque. In addition, compared with natural cooling, the water cooling makes the temperature of the MR fluid to drop by 32.7% under the same working condition. This is the first time that the cooling channel is set up in the cylinder-type MR transmission device, which will provide a solution for the higher power transmission capacity by MR fluid.

Multi-Objective Optimization in the Presence of OGIPFC Using NSMMP Algorithm

Background: Customers expect quality, uninterrupted power with cost-effective electricity in the latest trend. However, outages, severe storms, old infrastructure, and cost pressures can lead to ambiguity in power generation and transmission. To improve line power transmission capability, the right flexible AC transmission systems (FACTS) device may save millions of dollars. Methods: In this study, a FACTS controller named Optimal Generalized Interline Power Flow Controller (OGIPFC) was developed. Furthermore, for optimization, the Modified Marine Predator Algorithm (MMPA), which is a modification of the recently developed Marine Predator Algorithm (MPA). The optimum technique was used to evaluate a set of prioritized considered objective minimizations. A variety of factors must be maximized, such as generation cost, emissions, and power loss. Results: The performance of the proposed algorithm was analysed on benchmark test functions, and then single objective optimization problems of standard IEEE-30 bus system were solved and compared with the existing algorithms. The proposed algorithm was restricted to solving the single objective problem only, so it was further implemented with non-dominating sorting to solve the multiobjective optimization problem. The proposed multi-objective version is named as Non-dominating Sorting Modified Marine Predator Algorithm (NSMMPA), and it was validated on benchmark test functions and the IEEE-30 bus system. Conclusion: Finally, the OPF problem was solved with the incorporation of OGIPFC using the proposed methods, which resulted in better solutions and made the system more effective in operation.

Exploring the Potential of GaN-Based Power HEMTs with Coherent Channel.

The GaN industry always demands further improvement in the power transport capability of GaN-based high-energy mobility transistors (HEMT). This paper presents a novel enhancement-type GaN HEMT with high power transmission capability, which utilizes a coherent channel that can form a three-dimensional electron sea. The proposed device is investigated using the Silvaco simulation tool, which has been calibrated against experimental data. Numerical simulations prove that the proposed device has a very high on-state current above 3 A/mm, while the breakdown voltage (above 800 V) is not significantly affected. The calculated Johnson's and Baliga's figure-of-merits highlight the promise of using such a coherent channel for enhancing the performance of GaN HEMTs in power electronics applications.

Open-Circuit Fault Diagnosis and Tolerant Method of Multiport Triple Active-Bridge DC-DC Converter

The triple active-bridge (TAB) DC-DC converter, as a representative multiport converter, is widely used in DC distribution system. The open-circuit fault (OCF) of TAB seriously threatens the system safety operation. In this article, an OCF diagnosis and tolerant method is proposed for TAB converter to reduce the impact of OCF. The fault mode of TAB converter is first analyzed. Based on the analysis, an fault diagnosis method using the average value of bridge arm midpoint voltage and inductance current is proposed. To eliminate the DC bias and over-current caused by OCF, the symmetrical topology is constructed by modulation reconfiguration, and corresponding fault-tolerant operation strategies are proposed for OCF at different locations. When the OCF occurs on the bipolar DC bus side, the fault bus is cut off, while ensuring the power transmission between the monopolar bus and the critical load. When the OCF occurs on the critical load side, the bipolar DC bus could still supply its power. Based on the above strategy, the power transmission capability under OCF is guaranteed and the reliability of TAB converter is improved. Finally, the OCF diagnosis and fault-tolerant operation methods are verified through comparative numerical simulation and experimental results.

PV and QV analysis for finding the optimum location of FACTS device to investigate the effectiveness in KR power system using PSS/E

This paper presents the effect of Static Synchronous Compensator (STATCOM) device in power system for power flow and voltage stability analysis. The stability of power system is most important evaluation that is needed to be considered under various contingency states. This paper presented Power-Voltage (PV) and Reactive power-Voltage (QV) analysis which have been widely used in steady state of power system in normal operating condition and gives important details about the loading of the system and voltage stability. The shunt and series compensation can be used to increase the voltage and flow in the power system. Kurdistan Region Power System (KRPS) used to verify the effectiveness and performance of STATCOM in power system. PSS/E proposed as power system software for KRPS. The result shows that the proposed Full Newton Raphson (FNR) method spends less execution time and the optimum placement for STATCOM for enhancing static voltage stability margin and improves the power transmission capability of the line is the 'weakest bus' of the system.

Power quality improvement of a proposed grid-connected hybrid system by load flow analysis using static var compensator

Renewable resources are most effective for sustainable development of society and economically efficient for small-scale power generation. However, grid integration is challenging because of the randomness of the source effects on power system parameters. This work proposes power quality enhancement by incorporating Static VAR Compensator (SVC) in a grid-integrated renewable hybrid power system. SVC is one of the shunt type Flexible AC Transmission Systems (FACTS) devices that is adopted in this system for the compensation of reactive power requirement. The proposed hybrid system for the Rohingya Refugee camp is energized by a wind and solar based sources. The objective is to enhance the overall bus voltage profile by minimizing both real and reactive power losses as well as boost the power transmission capability of the entire system. Different case studies have been considered by changing the source availability and generation supply for load flow analysis using ETAP software. Moreover, critical system parameters such as bus voltage, power transfer capacity, and power losses have been reported during the inactive time of one or both renewable sources. The results obtained without SVC have been compared against the ones with the presence of SVC. Our analysis reveals that, as a result of using SVC, the voltage profile improves by 2.9–3.3%, branch loss reduces by 2.1–2.4%, and power transfer capability enhances by 7.5–9 units.

Research on Double LCC Compensation Network for Multi-Resonant Point Switching in Underwater Wireless Power Transfer System

This paper introduces a control method suitable for AUVs to transmit underwater radio energy that improves the stability of AUV charging under water based on double LCC compensation. The coupling coefficient decreases with the rise of the coil offset in the underwater wireless power transfer system, such that the power transmission capability is reduced. To solve the above-mentioned problem, a double LCC resonant compensation network impedance characteristic is proposed in this study through the analysis of the double LCC resonant compensation network. To be specific, the wireless power transmission method for multi-resonant point switching of the LCC compensation network is developed. The multiple resonance points of the developed method are not correlated with the load impedance in the double LCC resonance compensation network, and the multiple resonance points are consistent with the power transmission characteristics. Moreover, the appropriate resonance frequency is matched based on different coupling coefficients, and the multi-resonance points are switched to each other to increase the system’s transmission power and transmission efficiency. As revealed by the results of the simulation and experimental studies, the double LCC compensation network with multi-resonance point switching is capable of achieving the output characteristics of constant-voltage/constant-current of the wireless power transfer system, reducing the system current harmonics effectively, and enhancing the power transmission capability and anti-offset capability.

Fault current analysis and active current limiting strategy for hybrid cascaded LCC/MMC HVDC system

The hybrid cascaded LCC/MMC high voltage direct current (HC-HVDC) system is a prospective topology that can avoid the commutation failure problem of LCC-HVDC while ensuring bulk power transmission capability. However, the complex topology results in different DC fault characteristics at the receiving end, which brings challenges to fault detection and current limiting technology. As a result, it is of great theoretical importance to investigate the fault characteristics of the HC-HVDC system and propose the corresponding fault current limiting strategy. Firstly, this paper simplifies the equivalent discharging circuit of the hybrid cascaded LCC/MMC inverter into a first-order RL circuit by assuming the firing-advance angle is constant after fault, and proposes the fault current expressions by Laplace transform. Secondly, by changing the insertion sequence of submodules, an active fault current limiting strategy based on the submodule sorting algorithm (SMS-FCL) is proposed, which can accomplish fault current suppression, reactive power and DC voltage support, and energy loss reduction simultaneously. Moreover, the proposed SMS-FCL can cooperate with other FCLs to further suppress the fault current, and the cooperation prerequisites are analyzed. Finally, an LCC-LCC/MMC HVDC system is built in PSCAD/EMTDC to validate the accuracy of the proposed fault current expressions and the effectiveness of the current limiting strategy.

Multifunctional carbon/epoxy composites with power transmission capabilities

This study evaluates the power transmission of multifunctional composites with embedded conductors. The electrical conductors were constructed by braiding copper strands with Para-aramid fibers into a tape configuration, then placing these tapes within carbon/epoxy prepregs to create a multifunctional structure. Experiments were performed on these multifunctional composites under tensile loading conditions. During experimentation, the conductive tapes were incorporated within an electrical bridge to record their resistance change as a function of mechanical strain. The Digital Image Correlation (DIC) technique was used to obtain in-plane displacements and strains as a function of time. In addition, low-speed flight condition experiments with an airfoil shape composite system were carried out in a wind tunnel to study the temperature performance of these structures while under high currents. Computational models were then created to expand the experimental efforts and evaluate the system’s multiscale performance. Experimental results show that the mechanical load on the conductive tape is mainly carried by the Para-aramid yarns, leading to a relatively consistent electrical performance and airflow over the wind foil providing efficient power transmission. Lastly, the computational models showed consistency in the electrical/mechanical results and established a framework for analyzing multi-functional structures (MFS).

Negotiation of the global grid inspection UAV with random delay uncertainty in an information communication network based on a robust fault tolerance mechanism

To accurately simulate the interference mechanism of information communication between unmanned aerial vehicles (UAVs) in the future global grid system, a type of control based on dynamic simulation of the satellite communication network and robust fault tolerance with a stochastic delay uncertain network system is proposed. Based on the imaginary future of the global energy Internet, with unknown information and communication interference, we established a UAV model from sensor to actuator network delay using a robust, fault-tolerant control algorithm and a satellite communication network model that combined the controller’s mathematical model. The simulation results showed improved power transmission capability and communication coverage ability of UAVs by using the network fault-tolerant control mechanism with uncertain network delay and information communication interference. The stability and anti-interference performance was also significantly improved. This algorithm provides a strategy for the future development of global energy Internet.

Experimental Validation of a Mitigation Method of Ferranti Effect in Transmission Line

Electric power transmission networks should be operated in efficient, safe, and reliable conditions. To improve the stability and transfer capability of power transmission, it is necessary to mitigate the Ferranti effect. This paper investigates the impact of increasing the length of the transmission line on its receiving end voltage under no-load conditions. A variable shunt reactor compensation for transmission lines is used to control the voltage level at different lengths of the transmission line. The proposed method demonstrates that the value of the shunt reactor required to maintain the receiving end voltage can be estimated. Moreover, the system is modeled using the PowerWorld simulator, and the effectiveness of the proposed model has been verified by experimental results. The experimental results demonstrate the efficiency of the proposed methodology and match the simulation results, which are then validated by simulating the WSCC 9-bus and IEEE 30-bus test systems.

An Improved Hybrid Parallel Compensator for Enhancing PV Power Transfer Capability

This article proposes an improved hybrid parallel compensator (IHPC) for enhancing the power transfer capability of a photovoltaic (PV) grid-connected inverter. A thyristor switched capacitor (TSC) module is used in series with a conventional inductive-coupling voltage source inverter to reduce the dc-link voltage. Under a low dc-link voltage, the voltage across the insulated gate bipolar transistor (IGBT) will also be low, which will reduce the voltage stress of the IGBT, thereby improving the reliability and reducing the loss of the voltage resource inverter. First, the mechanism of reactive compensation for improving the PV inverter power transmission capability is analyzed. Then, the circuit configuration and operating principle of the IHPC are introduced. After that, an optimal control strategy for the IHPC is proposed to address the resonance problem caused by the TSC connected in series with the L filter and to improve the compensation performance of the IHPC. Finally, the effectiveness of the proposed IHPC and the control method is validated by the simulation and experiments. The results show that the IHPC with optimal control strategy can achieve continuous reactive power compensation under a low dc-link voltage, thereby enhance PV power transfer capability.