High Reliability Of Power Supply Research Articles

Research on degradation analysis and health condition assessment method of phase shifter

Abstract In high-power, high-reliability power supply systems, the switching operation of power devices is driven by phase shifters. Degradation or failure of the phase shifters leads to power device shoot-through and other failures, and reduces the power devices’ service lifetime. Aiming at the problem of phase shifter condition monitoring, a degradation model is proposed by analysing the degradation mechanism and aging process of the sensitive key components of the phase shifter, and then a health condition monitoring method with multi-dimensional features is presented in this paper. The multidimensional feature vectors in the time domain are extracted from the output voltage signals of different aging stages, and the time-domain feature separability of different health conditions is verified. Then the deep neural networks identification model based on deep learning technology is proposed to recognize the health condition of phase shifter. At last, the performance degradation simulation and experimental evaluation show that the proposed method can identify the phase shifter health conditions more accurately, and the accuracy rate can reach 95.892%.

Minimizing the Effect of Integrating Wind Farms on Transmission Power Systems

Expanding the renewable energy sources usage in power systems will help the government meet its energy policy goals of lowering emissions, ensuring high power supply reliability, and promoting spot markets with high competitivity. However, due to the intermittent nature of these sources, this will necessitate the mitigation of network vulnerabilities. High wind energy penetration in the grid could have an impact on the system frequency, voltage, real and reactive power response, and power quality of the system. The main objective of this paper is to investigate how the integration of wind farms in the Jalan Bani Bu Ali (JBBA) area will affect Oman's main interconnected system (MIS). Results show that the effect is minor on voltage and frequency stability by all disturbances taken into account.

Mobile energy storage systems with spatial–temporal flexibility for post-disaster recovery of power distribution systems: A bilevel optimization approach

In recent years, the damage to power distribution systems caused by the frequent occurrence of extreme disasters in the world cannot be ignored. In the face of the customer’s demand for high power supply reliability and high power quality, it is urgent to establish a resilient distribution network that can not only resist extreme disasters and quickly recover the power distribution system loads, but also ensure a high voltage quality of the distribution system during recovery process. Therefore, mobile energy storage systems with adequate spatial–temporal flexibility are added, and work in coordination with resources in an active distribution network and repair teams to establish a bilevel optimization model. The objective of the upper-level optimization model is minimum the total load curtailment of the distribution system after the disaster. And the objective of the lower-level optimization model is minimum the voltage offset of power supply buses during the recovery stage. A modified IEEE 33-bus distribution test system is used to verify this model. The simulation results show that the bilevel optimization strategy proposed in this research can effectively reduce the voltage offset during the recovery process of distribution systems, and ensure the minimum total load curtailment simultaneously.

Adaptive power supply system in plot with artificially complex profile

The paper deals with the issues of energy saving in the railway section, which has a tunnel with a double longitudinal slope, which limits the capacity of trains due to a decrease in the rated voltage by more than 10%, which negatively affects thermal and transient electromechanical processes. The practicality of voltage regulation using the existing installation of series compensation is shown; it is proposed to use an additional installation of parallel reactive power compensation, with automatic voltage regulation of the power transformer under load. The principle of self-tuning adaptive regulation is applied, establishing the optimal power supply mode according to the criterion of minimum losses, which has high reliability and cost indicators of traction power supply.

Discussion on the anti external force damage technology of power cable

With the accelerating process of urbanization and the increasing social power consumption, power cable, as an important part of the power system, has the advantages of high power supply reliability, large transmission capacity, less land occupation and less vulnerable to the influence of the external environment. However, urbanization construction is accompanied by a large number of municipal construction, which causes great external breaking pressure on the reliable power supply of power cables. Therefore, the effective anti external breaking monitoring and early warning of power cables can reduce the losses caused by cable external breaking. This paper mainly introduces the cable anti breaking monitoring system, which captures the vibration signal to identify the signal source, such as piezoelectric sensor, sound sensor and optical fiber sensor. This paper focuses on the working principle of three distributed optical fiber anti burst systems based on OTDR (optical time domain reflection), Mach-Zender interference and Michelson interference, summarizes the characteristics and application scope of each method, analyzes the existing problems of power cable anti burst monitoring and early warning technology at the present stage, and gives the summary and prospect.

Model-based techno-economic evaluation of power-to-hydrogen-to-power for the electrification of isolated African off-grid communities

Mini-grids are expected to be the least cost option to electrify more than half a billion people living predominantly in isolated communities in sub-Saharan Africa. Providing a high reliability of power supply to satisfy paying customers is vital for the challenging business case of mini-grid owners. Therefore, renewable-based mini-grids of the third generation commonly include either diesel generators or battery storage for backup power supply.Power-to-hydrogen-to-power (P2H2P) is a promising alternative to overcome technical, financial, and social shortcomings of diesel generators and batteries. Previous research highlights the challenging economic competitiveness of P2H2P in specific case studies only. Here, we conduct a model-based techno-economic analysis on an archetypal representative mini-grid to compare the economic performance of P2H2P against the diesel generator and battery storage. We identify key parameters decisive for the competitiveness of P2H2P via sensitivity analysis.Under today's conditions, P2H2P is financially viable in 100 % decarbonized mini-grid systems. Ongoing trends of increased fuel price and P2H2P technology improvements must continue to achieve economic advantages of P2H2P over the diesel generator. However, P2H2P is competitive in locations in which the diesel price is higher than 2.6 USD/l or when P2H2P investment costs drop by >50 %, which is expected beyond 2040. Sensitivity analysis shows that increasing P2H2P system efficiency can substantially benefit the economic performance. Seasonal variations on the African continent are insufficient to create exploitable advantages of P2H2P against the short-term storage of batteries.The results suggest especially larger future PV mini-grids to combine battery storage and P2H2P rather than including common diesel generators or only including batteries when trends towards cheaper and more efficient technologies continue and diesel prices increase. Future work should investigate economic effects of the unique multi-usability of hydrogen on the mini-grid system, such as the usage as clean cooking fuel.

Capacity optimization and feasibility assessment of solar-wind hybrid renewable energy systems in China

The solar-wind hybrid renewable energy systems, including wind farm, photovoltaic (PV) plant, concentrated solar power (CSP) plant, electric heater, battery, and bidirectional inverter, are analyzed in 36 typical locations in China. The effects of wind and solar energy resources on power supply reliability and economy and the optimal installed capacities are analyzed. The regions in China recommended for the development of the systems are given. Results show that the levelized cost of energy (LCOE) of system in Huade can be as low as 0.1 $/kWh when 90% of annual load demand is met. The wind speed and solar irradiation have a major effect while the complementary characteristics of wind and solar energy have an auxiliary effect on power supply reliability and cost of the system. Compared with the system in Tongliao, the LCOE of system in Qiqihar with lower wind speed and solar irradiation intensity is reduced by 9.8% due to the better complementary characteristics of wind and solar energy. For systems in locations with different wind and solar energy resources, the wind farm or PV plant is still the technology with the greatest cost advantage but the worst power supply reliability. The electric heater with thermal energy storage and power cycle is an essential factor to greatly improve power supply reliability economically. Meanwhile, one of the solar field and battery should be integrated into the system according to the direct normal irradiance conditions. When high power supply reliability is pursued, the CSP plant is recommended to be introduced in most regions. Moreover, the commercial promotion of CSP plant brings the most significant economic benefits to the system. As the CSP plant cost is reduced by 30%, the LCOE of system is reduced by 20.4%.

Configuration optimization and energy management of hybrid energy system for marine using quantum computing

Improving the technology of hybrid energy systems is an important development direction for the greening of ships, the configuration optimization and energy management of ship hybrid energy system is vital to enhance the marine electric power system reliability, economic efficiency, and sustainability. Focusing on this problem, this paper has carried out a study on the multi-objective configuration optimization method (COM) and energy management strategy (EMS) for ship hybrid energy system based on quantum computing. First, the mathematical model of distributed power modules of the hybrid energy system is established, and a configuration optimization objective function that aims at low-cost, long equipment life, and high reliability of power supply is constructed. Then, the combination with fuzzy rules and quantum multi-objective artificial bee colony algorithm to solve the objective function, the configuration scheme satisfying multiple constraints is obtained. On this basis, an energy management optimization objective function that meets both low-cost operation and maximum clean energy utilization for ship electric power system is established, the objective function is optimized in multi-objective quantum particle swarm optimization (QPSO) algorithm, and the real-time optimal scheduling for hybrid energy systems of the ship is realized. Experiments on simulative navigation data verify the feasibility of the multi-objective configuration optimization method using the quantum artificial bee colony (QABC) algorithm. Furthermore, energy management experiments with different strategies, experimental results show that the energy management strategy proposed in this paper outperforms other methods- and effectively reduces the operating costs, fuel costs, and pollutant emissions of marine power system, meeting the environmental requirements of the Energy Efficiency Operating Index (EEOI) for ships.

Optimal deployment of feeder remote terminal units in distribution networks to improve power supply reliability

Deploying feeder remote terminal units (FRTUs) in the distribution network and then integrating them into existing manual switches (MSs) can facilitate automatic locating of faulted sections and rapid isolation from faults to improve the power supply reliability. However, the fault management process, including fault location, fault isolation, and service restoration, is usually simplified in traditional FRTUs deployment methods. In particular, the fault isolation and service restoration operations are usually modeled individually without considering the FRTUs operation during the whole fault management process in these traditional methods. In this paper, the FRTUs in the potential service restoration paths for the customers are ruled out to avoid unnecessary power outage, and the effect of FRTUs operation on the fault management process is analyzed and discussed in branched distribution networks. Secondly, a quantification analysis model considering FRTUs operation is built to obtain the accurate interruption time of the distribution network. Thirdly, the quantification model is used to obtain the revenue generated by interruption cost reduction for the deployed FRTUs. Finally, an optimal deployment model of FRTUs in mixed-integer nonlinear format is constructed and solved efficiently by the software LocalSolver, which combines heuristic techniques and stochastic search algorithms. The new method is compared with the traditional FRTUs deployment method in the CSG 53-node test system, and the results show that the proposed method can achieve greater return on investment and higher power supply reliability.

Research on cable partial discharge detection and location system based on optical fibre timing

Partial discharge (PD) is an important index to reflect the running state of cables. According to the characteristics and propagation mechanism of cable partial discharge signal, a cable partial discharge detection and location system based on optical fibre time synchronisation technology and travelling wave double terminal location principle is developed. The system has high detection sensitivity, high reliability, real-time detection, diagnosis and positioning of cable discharge power supply. The experimental results show that the positioning accuracy of the cable partial discharge source can be effectively improved based on the fibre timing and double terminal positioning technology, and the positioning accuracy can reach 1%; the method studied in this paper can meet the requirements of the accurate location of the partial discharge source of the cable, Gil and other equipment.

Optimizing the sizes of wind and photovoltaic plants complementarily operating with cascade hydropower stations: Balancing risk and benefit

The complementary operation of wind, photovoltaic (PV) with hydropower stations has the potential to increase the consumption of renewable energy into the power grid. However, challenges remain to optimize the sizes of wind and photovoltaic plants integrated into the cascade hydropower stations. In this study, a size optimization method is proposed considering the balance of operation risk and benefit. First, a multi-scale nested joint operation model considering long-term, short-term and real-time complementary strategies, notably including the consideration of the forecast uncertainty of wind-PV output, is developed to simulate the operation of the hybrid system. Then, the optimal sizes are determined by a refined evaluation of the operation risk and benefit of the hybrid system. A case study in the Yalong River basin in China reveals that (1) the proposed multi-scale nested joint operation model can ensure not only high long-term power generation benefit, but also high power supply reliability; and (2) an appropriate wind-PV-hydropower size can achieve a higher power generation benefit and a lower load loss risk.

Mesh Planning Optimization for Urban Distribution Network with High Reliability

Modern distribution network has a huge volume and a wide range of points, so the difficulty of construction and transformation of distribution network often lies not in technological innovation, but in the operability of planning scheme, adaptability and flexibility of network structure. Therefore, an optimization model of mesh planning for high reliability power supply in urban power grid is proposed. Firstly, the planning process is optimized to avoid the cyclic adjustment of power supply mesh and power supply unit division. Secondly, a target network architecture and power supply unit partition model for medium-voltage power grid are proposed, which can meet the double power demand of important power users and ensure no cross-supply between units. Finally, an example of mesh planning in a city center in Hubei Province of China is given, and the application of the optimization method is described in detail. The results show that the method is easy to carry out, and effectively improves the reliability of power supply in urban power grid.

Determining 150kv transmission tower route using FAHP method

PT. Vale Indonesia Tbk (PTVI) is a mineral mining company that produces nickel as its main product. PTVI requires high reliability of power supply so that it can produce nickel to the specified target. One of the important equipment to maintain the availability of electricity is the transmission tower. Failure of the transmission tower will have a disastrous effect on nickel production operations. PTVI will lose 165 MW in case of failure on the Larona transmission tower line to plant site and 200 MW on the Balambano transmission tower line to the plant site. Therefore, PTVI will build a new 150kV transmission tower line from Larona switchyard to Balambano switchyard to support the availability of sustainable electricity. The method to be used to determine the best alternative transmission tower route by considering multiple criteria is Fuzzy Analytical Hierarchy Process (FAHP). The results of each alternative are 0.477 for the North route, 0.364 for the Middle route, and 0.159 for the South route. The authors recommend the management of PT. Vale Indonesia, as the owner and operator of the hydroelectric power station, chose the north route for the planned construction of the 150kV transmission tower.

Analysis on burning failure of main transformer in 220kV substation

Neutral point ungrounded three-phase system is widely used in 10kV and 35kV low-voltage systems because of its higher power supply reliability. When the single-phase grounding short-circuit fault occurs in the system, the other two phases can continue to operate for a period of time to ensure the reliability of power supply. However, when the system operates under single-phase grounding fault, arc grounding overvoltage is easy to occur, which may damage electrical equipment or develop into phase-to-phase short circuit. This paper analyses a burning accident of main transformer caused by arc grounding overvoltage in 220kV substation, obtains fault recording information, points out fault causes and puts forward corresponding preventive measures.

Single-Phase Fault Line Selection in Distribution Network Based on Signal Injection Method

The distribution network with small current grounding mode can ensure high power supply reliability, but it is difficult to locate single-phase grounding fault line. Most of the faults in distribution network are single-phase to ground fault. It is important to locate the fault line timely and accurately for the normal operation of the power grid. In this article, a fault line selection method based on signal injection is proposed. The dynamic selection of parameters and injection frequency in real-time monitoring distribution network by injection method is analyzed. The accuracy of signal frequency domain conversion is improved by using all phase Fourier transform. Taking the active power consumption of injected signal after fault as the criterion, the accuracy of line selection is improved. Through theoretical analysis and simulation, as well as experiments in a 600V distribution system, the fault line can be accurately selected.

Fault Location Method for Two-Terminal Untransposed Overhead Lines in Distribution Networks Measured by μMPMU

With the rapid development of distribution networks, two-terminal overhead lines have been used on a large scale for higher power supply reliability, thus the fault location has attracted much attention. Accurate fault location is helpful to shorten the outage time and improve the economy of operation greatly. However, since insufficient standardization of equipment selection and poor management, line parameters are usually inaccurate or even unknown, mature fault location methods based on impedance can’t be applied anymore. Also, the asymmetry caused by non-transposition in distribution networks affects the accuracy of fault location. This paper proposes a fault location method for two-terminal untransposed overhead lines without requiring line parameters. Firstly, this paper considers parameter asymmetry, and the mutual impedances between the three phases are set as different values. Secondly, the location equations rely on three-phase networks, then the self-impedance and mutual impedances are regarded as unknowns and solved directly. Finally, this method takes the average value of fundamental frequency components from different data windows, which reduces error and improves accuracy. The simulation results show that the fault location method has high accuracy, and can effectively overcome the influence of unknown line parameters and non-transposition.

Joint Sensor Selection and Energy Allocation for Tasks-Driven Mobile Charging in Wireless Rechargeable Sensor Networks

Wireless power transfer (WPT) has emerged as a promising paradigm to charge devices due to the high reliability and efficiency of continuous power supply. Recent studies usually focus on relatively general charging patterns and metrics but neglect the collaborated task execution of nodes that incur charging inefficiency. In this article, we respect the energy requirement diversity among nodes to investigate the collaborated and tasks-driven mobile charging problem. Our goal is to maximize the overall task utility that concerns sensor selection and task cooperation. To address this problem, we propose a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(1-1/e)/4$ </tex-math></inline-formula> -approximation algorithm. First, we propose a novel energy allocation scheme with a specific theoretical analysis of the submodularity and gap property for the surrogate function. Then, we approximate the traveling cost to transform the formulated problem into an essentially monotone submodular function optimization subject to a general routing constraint and propose a greedy algorithm to address this problem. We conduct extensive simulations to validate our theoretical results and the results show our algorithm can achieve a near-optimal solution covering at least 84.9% of the optimal result achieved by the OPT algorithm. Furthermore, field experiments in an office room and a soccer field environment are implemented, respectively, to validate our proposed algorithm.

The Suppression of Voltage Overshoot and Oscillation During the Fast Recovery Process From Load Short-Circuit Fault for Three-Phase Stand-Alone Inverter

When a three-phase stand-alone inverter feeds several loads simultaneously, to ensure high reliability and continuity of power supply for the large load network, the inverter needs to operate continuously, even during faulty conditions. Moreover, the inverter should provide large enough current by switching from the voltage control mode (VCM) to the current control mode (CCM) to trigger the circuit breaker connecting the short-circuit fault branch to recover the power supply. Therefore, when a load short-circuit fault occurs, the inverter will switch from VCM to CCM. In CCM, the short-circuit currents can be controlled by the current-limiting strategy. Once the fault is cleared, to quickly supply the remaining loads, the output voltages should be restored to the rated voltage as soon as possible. However, the fast recovery process from the load short-circuit fault may cause significant voltage overshoot and oscillation. The voltage overshoot may lead to load damage, and the voltage oscillation may extend fault recovery time. To effectively solve the above problems, the voltage overshoot introduced by large fault current and postfault load impedance after fault clearance is first analyzed in this article, and then the suppression strategy based on the parallel virtual impedance is proposed. Second, the voltage oscillation introduced by the initial phase difference between the voltage references and the output voltages when the inverter switches from CCM to VCM is analyzed, and then the effective suppression strategy which can achieve seamless mode switching after fault clearance is proposed. The experimental results have been carried to verify the effectiveness of the proposed strategies.

Coordinated Control Strategy for Operation Mode Switching of DC Distribution Networks

Due to the advantages such as low line cost, low transmission loss, and high power supply reliability, DC distribution networks have become the main development trend for future distribution networks. In this paper, a typical DC distribution network with multiple voltage levels is considered as a research object. It is proposed that the interface converters between DC buses with different voltage levels be implemented through the series-parallel combination of full-bridge LLC resonant converters. To realize the decentralized self-discipline control of DC voltage under various working conditions, different slack buses are prepared according to the voltage ranges of the DC buses, and the voltage regulation modes of the DC distribution network are divided into main voltage regulation mode, backup voltage regulation mode, and off-grid voltage droop regulation mode. By introducing a voltage coefficient related to DC voltage deviation as a basis for mode switching, the voltage fluctuations caused by slow switching between control modes in the method of traditional voltage margin control is reduced, facilitating fast and smooth switching between different voltage regulation modes. Finally, a simulation model for DC distribution networks is constructed utilizing MATLAB/Simulink. Simulation results verify the effectiveness and feasibility of the proposed voltage regulation modes and switching methods for DC distribution networks. Finally, an experimental platform is also constructed to verify the feasibility of the mode switching method proposed in this paper.

Reliability Assessment on Typical Connection Modes of High Reliability Demonstration Area

In the process of construction and modification of distribution, choosing connection modes is a key link of network construction and plays a pivotal role in distribution network. In this thesis, firstly, the distribution network frame and its present situation in demonstration area is analyzed, and the shortcomings in present network are designed; After using the features of advanced distribution network frame in international metropolis for reference, the experience is concluded and four kinds typical connection modes which suit for demonstration area are designed; The characteristics and the scope of application of every typical connection modes are analyzed, the modification scheme according to the present distribution network frame in demonstration area is illustrated. Finally, the examples are taken as cases to illustrate that these typical connection modes are of high power supply reliability. With the constant rise of the require of power supply reliability, the connection modes in demonstration area will be widely used and extended gradually.