Double Bus Research Articles

Behaviour analysis of H‐bridge high‐voltage capacitor banks fault on 230‐kV substation using discrete wavelet transform

AbstractThe protection of traditional high‐voltage capacitor banks relies on an unbalance relay which operates when an internal fuse is blown. However, the unbalance relay cannot indicate the cause of the fault. Thus, an operator wastes time and human resources investigating the fault issues. In this paper, a fault which occurred in a 230‐kV power system of Electricity Generating Authority of Thailand was observed by performing simulations using the Power Systems Computer Aided Design (PSCAD) program. The study system based on the double bus station and 72 MVAR capacitor banks was installed in the form of a back‐to‐back topology. Three scenarios were considered: normal condition, fault occurrence in one capacitor bank and fault occurrence in both capacitor banks. Current characteristics such as the current phase and difference in unbalance current were considered. In addition, discrete wavelet transform was applied to solve the ambiguity of current generated from the PSCAD. The authors’ results suggest that identifying fault events using a coefficient of wavelet is more efficient than relying on the current amplitude. The findings mentioned in this paper can be applied in a traditional power system protection scheme to enhance a system's reliability.

Topology of Wind Power DC Collection Converter Based on Double Bus Structure and Its Power Balancing Control Strategy

Wind power collection technology is the key to grid-connected wind power generation. Compared with AC wind integration, DC wind power collection is more advantageous. Using a triple active bridge (TAB) converter as a submodule, this paper proposes a wind power DC converter topology and its control strategy for medium-voltage dc (MVDC) grid connection. The converter adopts a double bus structure, with the MVDC bus connected to the grid and the low-voltage dc (LVDC) bus handling the mismatched power. It has independent maximum power point tracking (MPPT) control, power balancing, and autonomous voltage balancing on the output side. The converter system is simulated and verified on the MATLAB/SIMULINK software platform. The simulation results show the effectiveness of the control strategy and the ability of the converter to operate stably under multiple conditions.

Double bus failure protection based on zero negative sequence power directional element discrimination

After the fault circuit breaker at the end of the long line of the large mode operation system fails, the composite voltage sensitivity of the 220 kV and above double bus connection failure protection is insufficient, and the line release complex voltage locking function needs to be switched on and off manually, which cannot be automatically adapted after the system mode changes. To solve this problem, the compound voltage locking logic is cancelled, and the zero negative sequence power direction discrimination is used to simplify the startup failure circuit, which improves the adaptability and reliability of line failure discrimination under various operating conditions.

Double Bus Provider Asymmetrical Half Bridge Converter With a Resonant DCX-Derived Auxiliary Circuit to Supply a LED-Based VLC Postregulator

The wide and settled use of Light-Emitting Diodes (LEDs) in lighting has made Visible Light Communication (VLC) an interesting option. Given the way LEDs are driven in VLC, the Two-Input Buck converter fits perfectly as a post regulator for VLC-LED lamps. Its main drawback is that it needs two input voltages with specific requirements tied to the VLC feature. One needs to be regulated according to the LEDs knee voltage thermal drift, while the other needs to be constant. With the objectives of avoiding complex circuits with cross regulation and using two converters performing the bus provider, the present work proposes a converter with two outputs that meet those voltage requirements. This converter is the integration of an Asymmetrical Half Bridge converter and a resonant unregulated Half Bridge converter. This integration is achieved thanks to the primary side similarity of both converters and the integration of both transformers in one magnetic core, achieving a solution with fewer components. In addition, one output can be fully regulated by a standard control variable while the other remains naturally constant, and is independent from any control variable. This greatly simplifies the control stage, avoiding cross regulation while fully complying with the application requirements. This work presents the circuit concept and how it relates to the intended application. The principle of operation will be explained and used to define the wide operational region where the topology meets the requirements imposed by the application. To validate the proposed topology, a 45-W prototype is built and tested, archiving the output voltage requirements and an overall efficiency near 94%.

Analysis and Research on Power Supply Strategies of Electric Vehicles Based on Wind Farms

The widespread growth of electric vehicles could pose significant grid and charging infrastructure challenges, especially in areas with underdeveloped infrastructure. This has affected the ease of charging electric vehicles. In this paper, I design a power supply strategy for electric vehicle charging facilities based on wind farm power supply. In this strategy, a preliminary selection of line conductors is carried out, and several schemes are preliminarily determined. Further comparative analysis is made from the three aspects of conductor, tower type, and bus. Through the PowerWorld software, a simulation model is established for each scheme, and an optimal strategy that takes into account economy, security, and system stability is obtained (AAC 31.5 mm double split, tower A and bus 5). This can assist in the transformation of electric vehicle power supply and the construction of wind farm power supply facilities.

Research on Cabin Integrated Equipment Based on GIS

Through the research on the principle of GIS gas insulated switchgear, a GIS-based cabin integrated equipment method is proposed. The insulation characteristics and engineering calculations of SF6 gas are analyzed, which provides a basis for the selection of 220kV and 110kV equipment. Analyzed the applicability of 220kV equipment selection of HGIS equipment and GIS equipment in modular substations. At the same time, it compared the floor area and other indicators, and finally decided to adopt the GIS plan, further optimize the product structure and layout, and improve space utilization It can reduce the equipment footprint and make the layout of the power distribution device more compact. Through the comparison and analysis of the main wiring types of the 110kV single bus three section and double bus wiring, it is found that there are three aspects of reliability, flexibility and economy. Single-bus three-section is better than double-bus wiring, so 110kV is determined to adopt single-bus three-section wiring. Under the premise of meeting the requirements for power supply safety, reliability, and flexibility, 110kV electrical main wiring is optimized to achieve The purpose of simplifying operation and maintenance procedures and saving investment.

Research on 220kV Substation Main Electrical Connection Optimization Based on Life Cycle Cost Theory

As a key link of power transmission, substation main wiring plays an important role in improving the reliability of power supply in the grid. At present, the design of substation main wiring mainly is made with reference to the typical design schemes. However, due to the continuous development of load and the reliability requirements, the traditional wiring scheme may not fully meet the actual operation requirements. In response to this problem, a new main wiring idea is proposed, 3/2 circuit breaker wiring is added to the conventional double bus wiring scheme to form a mixed wiring scheme. The reliability of each scheme is calculated and analyzed. A certain 220kV substation with heavy load in Chengdu is taken as an example, the loss of social output value is considered, the comprehensive economy of the whole life cycle of the substation construction is calculated and compared, and finally the conclusion is drawn that the reliability and economy of the proposed scheme are the best.

확장된 토폴로지를 갖는 배전변전소의 지능형 고장복구 알고리즘의 연구

This paper propose an intelligent restoration algorithm for newly extended distribution substations equipped with double bus double brakers structure, which are widely used in Korean power systems. The complete hierarchical restoration process are proposed in detail including distribution buses which have extended topology. As the dramatic intelligent automation of power systems is in progress so far, it is anticipated that the results would be applied to IEC protocols in the future as well as the state estimation function for distribution substations.

DC‐link capacitor voltage balance strategy of independent double three‐phase common bus five‐level NPC/H‐bridge inverter based on finite control set

This study aims at the DC-link capacitor voltage imbalance problem of independent double three-phase common bus five-level neutral point-clamped/H-bridge inverter, which is applied to an electromagnetic launch system under instant high-power and high-current conditions. First, the traditional method of voltage balance strategy based on redundant vectors is described, and the key factors leading to the DC-link capacitor voltage fluctuation is analysed in detail. Second, the objective function is constructed to predict the variation trend of DC-link capacitance voltage difference. Third, an optimised voltage balance strategy is proposed. At first, the optimised strategy calculates the variation trends of the voltage difference for all three-phase switch vector combinations. Then, the results make up a voltage balance finite control set. At last, compare the results in the set to select the vector combination corresponding to the minimum variation for output. Finally, tested by the semi-physical real-time simulation platform, and the proposed optimised voltage balance strategy is verified effective for improving DC-link capacitor voltage imbalance and inhibiting the voltage difference fluctuation.

An Overview of High Impedance Differential Scheme, Design, Protection and Simulation for a 132 KV Double Bus Bar Single Breaker System

An Overview of High Impedance Differential Scheme, Design, Protection and Simulation for a 132 KV Double Bus Bar Single Breaker System - written by Mahmoud Said Mohamed Bedeir published on 2020/03/16 download full article with reference data and citations

Analysis and improvement on reliability of 66/11 kV distribution substation and its associated feeders: A case study of Lainchour substation in Nepal

Electric power interruption is becoming a day to day phenomenon in our distribution system. For distribution system to be effective there should be less outage in the system and if fault occur these faults should be cleared as soon as possible. Sustained power interruption occurs several times a day from few minutes to hours. Interruptions may be due to failure of substation equipment or failure of distribution network elements. This paper attempts to identify different causes of interruption and problems that customers in Nepal have been facing due to frequent planned and unplanned sustained interruptions by evaluating various reliability indices and parameters of Lainchaur distribution substation and its associated feeders operated under Nepal Electricity Authority. First, reliability analysis of substation configuration only is done followed by analysis of reliability improvement measures like use of double bus bar, parallel distribution feeders and underground cables in DIgSILENT PowerFactory only considering sustained failures of equipment and feeders. Calculated reliability indices like System Average interruption Duration Index (SAIDI), System Average Interruption Frequency Index (SAIFI), Energy Not Served (ENS) are compared for different cases so that it will be easy to make choice between options to the utility to upgrade/improve the system. Considering all feeders, result shows that main cause of interruption in the distribution system is failure of distribution lines showing 104 interruptions for total duration of 107 hours per annum in the system, followed by failure of distribution transformers indicating 19 interruptions for total duration of 47 hours per annum. Simulation result in DIgSILENT shows yearly total ENS of distribution system is high due to present configuration, and can be reduced by the use of parallel feeders and underground cables respectively. It is seen that ENS due to failure of substation components only is very low and huge revenues can be saved if auto-reclosures are used or a provision of charging feeders as soon as possible is made.

Computer Redundancy Management Technology Based on Non-Similar Platform

In order to study an efficient and reliable platform management computer, a non-similar platform management computer technology is designed. According to the structural characteristics of the computer management platform, a redundancy management strategy is developed. The redundancy management strategy of processor is studied. Then the priority order and voting strategy of four processors are determined, and several typical failure modes in practical work are discussed in detail. In order to verify the correctness of the synchronization strategy and redundancy management strategy, the principle prototype was tested, including the test of synchronization accuracy, typical debugging results and double redundant bus switching effect. The results show that the system runs stably and the four processor has good synchronization. It can achieve two fault works and three fault safeties, and it can realize bus switching.

Distributed power system stabiliser for multimachine power systems

Power system stabiliser (PSS) widely used to enhance the stability of power systems is based on the feedback of rotor speed error with respect to the rated value. However in many occasions, after the disturbances, it is desirable to re-synchronise all generators first rather than to make all generators back to the rated 50/60 Hz immediately. This study proposed a distributed power system stabiliser (DPSS) that aims to synchronise generators by the feedback of relative rotor speed errors of each generator with respect to its neighbouring generators. The proposed DPSS is analysed on a double machine infinite bus system, and shows that the proposed DPSS can enhance the stability of power systems by increasing the synchronising torque. To evaluate the efficiency of proposed method, the proposed DPSS is tested on three benchmark systems. The simulation results verify the efficacy of theoretical analysis, show the outperformance of DPSS over other PSSs, and demonstrate the superiority of re-synchronising generators over making them back to rated value in the post-fault. Communication issues have also been evaluated, which demonstrates the robustness of DPSS against both communication failures and random delays.

New optical differential protection algorithm applied in bus protection

In order to improve the speed and reliability of bus protection, people put forward the optical current transformer (OCT) replaced the traditional electric–magnetic current transformer. As OCT has no magnetic saturation, no band limits, and can accurately and quickly transform the full-waveform current signal in principle, the authors put forward a new optical differential protection algorithm which directly use the integral values of the operating current and the restraint current measured by OCT as the differential protection algorithm. The authors build 220 kV double bus protection model and simulate the actual fault current signal by Real Time Digital Simulator (RTDS). Then, the authors bring the fault current into the bus protection algorithm for verification, and analyse the simulation curves of restraint ratio. The simulation results prove the feasibility of the optical differential protection algorithm.

Study on Improving Reliability of 220kV Double Bus and Double Section Connection

Study on Improving Reliability of 220kV Double Bus and Double Section Connection

A Wavelet-Based Busbar Differential Protection

This paper presents a new wavelet-based busbar differential protection algorithm, named as 87BW function. The instantaneous current-based differential protection fundamentals are taken into account and the well-known 1-out-of-1 and 2-out-of-2 tripping logics are mapped into the wavelet domain. Operating and restraint wavelet coefficients energy of currents are computed, regarding station configuration and bus zones boundaries. Thereby, the proposed 87BW function can be properly used in both static and dynamic busbar configuration. Its performance was evaluated through EMTP-based simulations of faults in a 230 kV power substation with double bus single breaker configuration. The obtained results reveal it provides ultra-high-fast trip for internal and evolving external-to-internal faults, guaranteeing security for normal through-load and external faults as well, even in the case of early and severe current transformer saturation.

Add-drop double bus microresonator array local oscillators for sharp multiple Fano resonance engineering

Asymmetric resonances are currently the subject of considerable research efforts in photonic nanostructures. Here we propose a feasible method to achieve multiple Fano resonances and their control in an optical compound system consisting of an array of on-chip microresonators without mutual coupling and two parallel fiber waveguides side-coupled to the microresonator array by means of a local oscillator. We derive analytical and transparent expressions for the power transmission function summing over the two light transporting paths within the framework of quantum optics. It is clearly shown that introducing the local oscillator as an additional light propagating path plays an important role in the formation of narrow and multiple Fano resonance lineshapes. The power transmission spectrum through the combination of both the microresonator array and the local oscillator is very sensitive to the system parameters, for example, the intrinsic decay rate of the resonator, the phase shift factor of the local oscillator, the transmission coefficient of the fiber beam splitter, and the total number of the microresonators. Through detailed analysis, we identify the optimums for generating Fano resonance lineshapes. Also, we assess the experimental feasibility of the scheme using currently available technology. The proposed method is relatively straightforward as it requires only one local oscillator as one interferometer arm and it is mostly fiber-based. We believe that our work will help to understand and improve multiple Fano resonance engineering.

횡풍이 작용하는 속도로의 회전구간에서 도로의 편경사각이 주행차량의 전복사고에 미치는 영향에 관한 분석연구

최근 경기도의 혼잡한 시간에 교통 문제를 해결하기 위해 2층 버스 서비스가 검토되고 있다. 2층 버스의 경우 높이와 폭의 비율이 일반 고속버스 보다 1.16배 이상 크며, 2층 버스의 C.G 점이 일반 버스보다 높다. 2층 버스가 고속 주행 시 강한 측면 바람 상태에서 차선 이탈과 같은 주행 안정성 문제가 특히 심각할 수 있다. 본 수치 해석 연구에서는 고속 주행 중 측면 바람 조건 및 편경사 조건에서 2층 버스의 주행 특성을 검토 하였다. 주어진 주행 조건에서 버스의 동적 안정성을 평가하기 위하여, CFD 수치 시뮬레이션을 이용하여 모델 버스의 롤링, 피칭 및 요잉모멘트를 계산하고, 도로 위 주어진 주행 조건하에서 모델 버스의 복구 각 모멘트 결과와 비교 하였다. 이 연구에서 모델 버스는 직선 도로를 따라 이동할 때 어떤 측면 바람 상태에서도 안정된 상태에 있다는 것을 알게 되었다. 그러나 버스가 측면 바람 상태에서 곡선 도로를 따라 이동 중에 측면 바람 (15m/s)에서 선회 반경이 100m 미만인 곡선 도로를 통과할 때 버스는 불안정한 조건에 동적으로 도달 할 수 있고 버스가 뒤집힐 가능성이 있다. 그러나 어떤 주행 조건에서도 모델 버스가 차선 이탈 가능성은 낮았다. Kyeonggi Provincial Government is considering double decker bus service to solve the problem of heavy rush hour traffic. However, the height-to-width ratio is more than 1.16 times larger than that of a general high-speed single decker bus, and the center of gravity is higher. This could cause driving stability problems, such as turnover and breakaway from the lane, especially under strong side-wind conditions at high speed. In this numerical study, the driving characteristics of a model double decker bus were reviewed under side-wind and superelevation conditions at high driving speed. The rolling, pitching, and yawing moment of the model bus were calculated with CFD numerical simulation, and the results were compared to the recovery angular moments of the model bus to evaluate the dynamic stability under given driving conditions. As the model vehicle moves on a straight level road, it is stable under any side-wind conditions. However, on a curved road under side-wind conditions, it could reach unstable conditions dynamically. There is a chance that the bus will turn over when it moves on a curved road with a radius of gyration less than 100 m under side-wind (15 m/s). However, there is a very small chance of breakaway from the lane under any driving conditions.

A high performance reliable NoC router

Aggressive scaling of CMOS process technology allows the fabrication of highly integrated chips, and enables the design of multiprocessors system-on-chip connected by the network-on-chip (NoC). However, it brings about widespread reliability challenges.Aiming to tackle the permanent faults on the router components, we propose a high performance, high reliability and low cost router design based on a generic 2-stage router. Five fault tolerant strategies are employed in our reliable router. We exploit an ECC detection and virtual channel closing strategy for input buffer faults, a double routing strategy for the routing computation (RC) faults, a default winner strategy for the virtual allocation (VA) faults, a runtime arbiter selection strategy for the switch allocation (SA) faults and a double bypass bus strategy for the crossbar faults. Different from previous reliable routers, our design leverages the feature of pipeline optimization and routing algorithm to maintain the performance in fault tolerance especially under heavy network loads. Besides, our proposed router provides higher reliability with lower hardware consumption than previous reliable router designs.

On Improving Reliability of Shipboard Power System

Distribution system reliability, defined by the expected frequency and duration of load service interruptions caused by component failures, is shown to be dependent on the topology of the distribution network, as well as on the relative placement of loads and generators within the system. In a shipboard electrical distribution system, a network topology based on the breaker-and-a-half scheme is shown to confer greater reliability than equivalent distribution topologies based on the ring bus and double bus, double breaker designs. The overall service interruption rate in the breaker-and-a-half topology is 17.8% less than that in the ring bus topology and 40.0% less than that in the double bus, double breaker topology. Further, an optimized equipment placement configuration is algorithmically identified for the loads and generators within the breaker-and-a-half distribution network, further increasing reliability. The optimal equipment placement decreases the overall system interruption rate by 0.54%. The paper also determines an optimal location for additional in-feeds that should be connected to the ship's most critical loads so that maximum benefits to service reliability are obtained.