Separate Bus Research Articles

Optimal location and sizing of renewable distributed generations and electric vehicle charging stations

Many countries are aiming to replace gasoline-based vehicles with electric vehicles (EVs). The increasing adoption of EVs has led to a surge in the number of charging stations, significantly impacting the electrical grid with issues such as power quality degradation, increased losses, and voltage fluctuations. In response to these challenges, there is a growing interest in integrating distributed generation from unconventional and renewable sources into the grid to power EV Charging Stations (EVCSs). However, this integration poses new complexities, including increased power losses and voltage instability. Consequently, the optimal allocation and sizing of Renewable Distributed Generations (RDGs) and EVCSs have become critical planning considerations. This paper addresses these issues by formulating a multi-objective optimization problem aimed at minimizing power losses and improving the voltage profile of distribution systems. The study introduces several constraints, including the placement of EVCSs and RDGs at separate buses, and employs particle swarm optimization and cuckoo search algorithm to simultaneously determine the optimal locations and sizes of the RDGs and the optimal locations of the EVCSs. The effectiveness of the proposed techniques is demonstrated through simulations on IEEE 33 radial and meshed distribution systems, illustrating their capability to identify optimal configurations for integrating RDGs and EVCSs.

Integrated Transportation Case: Planning of Future Transport Infrastructure/Connectivity In Dar es Salaam

Urbanization poses significant challenges to transportation systems in rapidly growing cities like Dar es Salaam. This paper examines the potential of Bus Rapid Transit (BRT) and Intelligent Transport Systems (ITS) to address transportation issues in the Ilala municipality. Despite ongoing infrastructure projects, the city lacks a comprehensive master plan to support its projected growth. The research underscores the importance of integrating infrastructure improvements and ITS to optimize the BRT system in Ilala. The study begins with an analysis of the current transportation landscape, highlighting deficiencies in road networks and public transportation that lead to severe congestion and unreliable commutes. Key stakeholders are identified, and the necessity of their involvement in transportation planning is emphasized. The research questions focus on enhancing stakeholder engagement, integrating ITS, and improving road infrastructure design. A mixed-methods approach is employed, including literature reviews, case studies of successful BRT implementations worldwide, and primary data collection through interviews, surveys, and focus groups with various stakeholders. This comprehensive approach provides actionable insights for enhancing urban mobility in Ilala. Future recommendations include upgrading the BRT system to a Level 3 configuration, incorporating elevated BRT sections to separate bus lanes from other traffic, and optimizing the design of lanes, stations, and vehicles to improve efficiency. Additionally, the paper discusses the potential benefits of a well-implemented ITS, providing real-time information to commuters and enhancing overall transportation experience. By addressing these challenges, the research aims to improve the quality of life for Dar es Salaam residents, stimulate economic growth, and contribute to a more sustainable urban environment. The findings and recommendations offer a strategic framework for future transportation planning in Ilala and beyond

Development and research of uninterruptible power supply system for networks with supply voltage up to 24 V

Objectives. Due to the continuous rapid development of renewable energy sources, requirements for secondary power supply systems keep increasing from year to year. Productive uptime for end users is dependent on the efficiency and stability of the power supply system. Such systems should be able to distribute and store energy from renewable sources having various parameters and configurations. Therefore, the present work is aimed at developing technical solutions for efficient uninterruptible secondary power supply systems in low voltage DC networks.Methods. Advanced circuitry solutions are used for performing pulse conversions with high efficiency. The flexible hardware-software system is used for implementing the parameter control system.Results. An uninterruptible power supply for low-voltage DC networks is developed. The description of subsystems and calculations for all main elements including the power ones are given. Using a contemporary component base, the system prototype is assembled, configured, and measured by parameters. The presented solutions allow achieving the universality of the system in terms of the input and output voltage range. Support for the fast-charging Power Delivery protocol is integrated. As well as regulating the battery charging current and voltage, the Li+ battery charging controller permits changes in the number of chargeable cells. The monitoring and control unit monitors network parameters and controls the system automation. Using a microcontroller as the control device, it is possible to easily change control parameters by changing software settings. Dual redundancy of the module monitoring the built-in battery parameters is used to ensure the reliability and safety of system functioning. Support for the standardized I2C communication protocol with a separate power bus allows any necessary sensors to be connected for monitoring system parameters. External high-power devices controlled by a PWM signal may be added, if required. In the paper, the Li+ battery charging profile recommended by the manufacturer is provided.Conclusions. The designed system provides stable power supply to end users at a power consumption up to 40 W for at least 45 min. The automation demonstrates reliable operation.

Users’ Perceptive Evaluation of Bus Arrival Time Deviations in Stochastic Networks

This work is a report on research concerning transit service characteristics as seen from the users’ point of view. Users of two separate bus lines, operating in a shared/ common urban infrastructure, were interviewed at bus stops about their perception concerning headways of bus lines operation. An analysis was made regarding deviations between actual and scheduled bus arrival headway. Further statistical analysis was carried out to check factors giving rise to different perceptions. The operation of each bus line was registered, and corresponding service characteristics were compared with those perceived by the users. Based on these results, a model for bus line headways was proposed, incorporating the perception of deviations by the users. In conclusion, a reliable service, meaning smaller deviations, is more appreciated by the public than any service of shorter headways and less reliability.

BUS LANE IMPLEMENTATION STRATEGY

This paper proposes a methodology for bus lane allocation including different strategies, dynamic bus lanes, and exclusive bus lanes. Choosing the right solution depends on many factors, such as traffic flow, passenger flow, and time losses. Analytical or simulation models can be used to evaluate the effectiveness of a separate bus lane. Analytical methods are simple to use and provide results in a short time. Simulation models, unlike analytical ones, require much more time and data to prepare but they are also much more detailed and accurate data. Therefore, analytical models may be particularly needed in the first stage of planning work during which potential sections for separated bus lanes are indicated. In this article, the author proposed an analytical model based on the 6th edition of the Highway Capacity Manual, which can be used to assess the implementation of separated bus lanes in different strategies. The final model developed was calibrated using traffic measurement results collected in a Polish city. As a result of the work, the author proposed the calculation procedure of the assumptions and diagrams, enabling the assessment of the selection of the appropriate solution.

Enhancing the Utilization of Processing Elements in Spatial Deep Neural Network Accelerators

Equipping mobile platforms with deep learning applications is very valuable. Providing healthcare services in remote areas, improving privacy, and lowering needed communication bandwidth are the advantages of such platforms. Designing an efficient computation engine enhances the performance of these platforms while running deep neural networks (DNNs). Energy-efficient DNN accelerators use skipping sparsity and early negative output feature detection to prune the computations. Spatial DNN accelerators in principle can support computation-pruning techniques compared to other common architectures, such as systolic arrays. These accelerators need a separate data distribution fabric like buses or trees with support for high bandwidth to run the mentioned techniques efficiently and avoid network on chip (NoC)-based stalls. Spatial designs suffer from divergence and unequal work distribution. Therefore, applying computation-pruning techniques into a spatial design, which is even equipped with an NoC that supports high bandwidth for the processing elements (PEs), still causes stalls inside the computation engine. In a spatial architecture, the PEs that perform their tasks earlier have a slack time compared to others. In this article, we propose an architecture with a negligible area overhead based on sharing the scratchpads in a novel way between the PEs to use the available slack time caused by applying computation-pruning techniques or the used NoC format. With the use of our dataflow, a spatial engine can benefit from computation-pruning and data reuse techniques more efficiently. When compared to the reference design, our proposed method achieves a speedup of ×1.24 and an energy efficiency of ×1.18 per inference.

Optimizing bus line platform assignment across bus stations in Utrecht

Due to its increased popularity, public transport has grown considerably, which has resulted in more lines that are operated with higher frequencies. As a result, the current bus stations that are located in strategic places like city centers to serve as a hub are becoming too small. If there is no space to enlarge the station, then usually the best option is to create a second bus station close-by. This raises the problem of distributing the bus lines over the bus stations, such that good connections are offered to transfer passengers. We have considered this problem in the city of Utrecht, which is a middle-sized city in the center of the Netherlands. The central transit hub, which is located next to the central railway station, consists of several separate bus stations. The goal of the research is to minimize the total travel time for all passengers who want to transfer at the hub. Here we are not allowed to adjust the current timetable, and we have to take the capacity and vehicle limitations into account. To find out which journeys are made daily and by how many people we use data from a digital fare system. This results in passenger groups, and for each group we compute the relevant travel options given the current timetable. Thereto, the routes are split into an inbound itinerary, a transfer within the same bus station, and an outbound itinerary; the validity of a travel option depends on the assignment of the bus lines to the bus stations. We decompose the problem into first finding a distribution of the lines over the stations and then assigning them to a platform at the station of choice. In the first subproblem, we find the best set of transfers using Integer Linear Programming (ILP), resulting in a station assignment. In the second subproblem, for each station, we distribute the bus lines over the platforms. In this subproblem, there can be multiple lines assigned to a single platform, as long as there are never more vehicles at the platform simultaneously than physically fit. The goal is to maximize the comfort of the transfer passengers by assigning tight transfers to adjacent platforms; this problem is solved using ILP as well.

A global power quality index for assessment in distributed energy systems connected to a harmonically polluted network

ABSTRACT Renewable-based generation technologies are gradually making their way into modern delivery grids due to their various advantages, but power quality (PQ) remains a deciding factor for their satisfactory operation. The assessment of overall power quality performance of grid-connected renewable-based distributed energy systems (DESs) is undeniably a complicated process due to their susceptibility to load side and background PQ disturbances, as well as quite a few PQ disturbances produced by the distributed generator (DG) itself. The aim of this article to make the PQ evaluation of the identical rather streamlined by integrating the apprehensive PQ indices at separate bus groups along with the total PQ performances of separate bus groups in one composite index by making use of the analytic hierarchy process (AHP). The technique suggested for formulation yields a centralized global power quality index (GPQI) intended for three categories of bus, namely utility, load, and DG, as well as the overall system. The proposed GPQI is supposed to be exclusively ample to benchmark the global PQ performance of grid-connected DGs with respect to the customized threshold level, in addition to the PQ performance levels grading between the diverse DG systems differentiated by either resource forms or sittings in a large distribution power system. This kind of global index would significantly facilitate the PQ evaluation of grid-integrated DESs. In addition, it may also be extremely useful for distribution network operators (DNOs) to track and penalize DG operators for working inadequately on PQ perspective, and to inspire them to follow the best alternative across numerous power quality improvement (PQI) technologies. The proposed methodology’s applicability is developed and authenticated by applying it in MATLAB on a grid-integrated solar energy conversion system (SECS). The obtained values of GPQIs, by applying the proposed approach in the test system, for the utility, DG, load bus and overall system respectively are 1.530, 1.727, 1.719, and 1.659, respectively, indicating the poor PQ performance of the DG unit under study. The effects of background voltage distortion (BVD) on the utility side and nonlinearity level (NLL) on the load side on the proposed index are also thoroughly investigated. The simulation findings obtained at different NLL and BVD levels affirm the proposed approach’s efficacy in correctly indicating the status of overall PQ in the concerned DG system.

Allocating exclusive and intermittent transit lanes in dynamic traffic networks with connected and automated vehicles

Exclusive bus lanes (XBLs) have been widely discussed and implemented worldwide in recent years. An improved and more flexible transit lane management strategy—intermittent bus lanes (IBLs)—prove to be potentially more efficient and car-friendly than XBLs. The common benefit of XBLs and IBLs arises from the fact that they separate the bus and car traffic and hence eliminate the impacts of slowly moving buses on the car traffic. Compared to XBLs, the application of IBLs has not been broadly adopted in the real world so far except very few cases, because managing an urban IBL segment or area typically involves extra traffic signals and message signs and the switch between its regular and protected statuses could potentially cause unexpected traffic chaos and safety issues. The recent emergence of connected and automated vehicle (CAV) technologies, however, favors relieving these concerns and bring the dawn to a future application of this theoretically sound traffic control strategy. This paper is dedicated to evaluating the network performance of XBLs and IBLs and optimizing the networkwide configurations of these two strategies for future urban traffic networks where CAVs prevail. For this purpose, we formulate a system-optimal dynamic traffic assignment (SO-DTA) problem with car-exclusive lane segments, on the basis of a cell transmission model for separate car and bus traffic (CTM-SCB). By limiting its applicable context to morning commute networks and emergency evacuation networks, this model is set with only one real or virtual destination, which greatly eases its modeling and solution complexity. On the basis of the single-destination SO-DTA model, an XBL-based network design problem and an IBL-based network design problem are then both formulated into mixed integer programming models and solved by a discrete optimization solver, where the former problem statically configures bus lanes while the later one allows a dynamic allocation of bus lanes. Insightful findings obtained by applying the models and solver to a synthetic corridor network and a real commute network illustrate the great promise of these two lane-based strategies in mixed car and bus traffic management.

Mapping of bus travel time to traffic stream travel time using econometric modeling

Travel time is one of the most important traffic parameters for travelers, traffic managers, planners, and operators alike. Travel time estimation is a significant component of any intelligent transportation systems (ITS) operations. In countries like India, which are at a nascent stage of ITS deployment, one of the main hurdles is the lack of accurate and automated systems for travel time data collection. However, in most of the cities in India, public transit buses are equipped with global positioning system (GPS) devices providing rich bus travel time data. Privacy issues deter the use of such GPS devices in private vehicles present in the stream. Hence, estimating the stream travel time using buses as probes is a relevant problem. In countries like India, where a heterogeneous and less lane disciplined traffic condition exists and the buses have to share the road space with other vehicles (no separate bus lanes); this mapping of bus travel time to stream travel time becomes challenging. The present study attempts to estimate stream travel time using buses as probes in a heterogeneous and less lane disciplined urban traffic scenario. Preliminary analysis of the collected travel time data indicated significant variability across time and links. Panel modeling can capture both this cross-sectional and time-dependent behavior and hence is used in this study. The estimation model is corroborated with field data and the performance is found to be satisfactory.

Selecting grounding points to reduce the interference level of the signal of high-impedance measuring channel

The study was carried out (2020) to reduce the effect of electromagnetic interference generated by a device for the formation of temperature effects based on Peltier element on a plant biopotential meter. Four variants of equipment grounding circuits are considered in the absence of a separate grounding bus for power equipment; graphs of biopotential signals are given. The type of interference that the device for the formation of temperature effects induces on the biopotential measurement channel is shown. The control unit case for the temperature-controlled stage based on Peltier element and the power cable shield for connecting Peltier element to the control unit must be grounded at a separate point from the biopotential meter. Biopotential meter electrodes should be grounded as far as possible from the control unit case and at a separate point from the grounding of the plate of the temperature-controlled stage. Recommendations are given for the grounding of high impedance input measuring devices and the power equipment emitting powerful inductive interference and causing interference in the grounding bus located in the same laboratory room, in the absence of separate grounding for power equipment. To reduce interference to an acceptable level, in addition to the selection of the grounding point, filtering is required. If the grounding point is selected incorrectly, a signal with a high level of interference is present at the filter output. The application of the proposed recommendations for grounding a device for the formation of a temperature effect based on Peltier element and a biopotential meter makes it possible to assess the response of a plant placed on the temperature-controlled stage to a temperature effect and not complicate programmed filtering of the signal received by the biopotential meter.

Robust Backstepping Speed Controller of a Doubly Fed Induction Motor using State-Space Nonlinear Approach

The aim of this paper is an efficiency Backstopping speed controller with direct stator flux orientation of doubly fed induction motor (DFIM) fed by two PWM inverters with separate DC bus link, the Backstopping controller is designed based on the Lyapunov stability theorem, by introducing the approach for decoupling the motor’s currents in a rotating (d-q) frame, based on the state space input-output decoupling method. The purpose is therefore to make the speed and the flux control resist to parameter variations, because the variation of parameters during motor operation degrades the performance of the controllers. The proposed approach is analysed by Simulink/Matlab environment. The simulation results show good performance and robustness.

A Generalized Input Impedance Model of Multiple Active Bridge Converter

The electrical power distribution system (EPDS) of the more electric aircraft (MEA) is a fundamental component that needs to be efficient and resilient. The commonly considered architectures feature separate buses to achieve separation between different subsections of the EPDS. Although effective, this implies an over design, since all subsections are sized for the local worst case scenarios. In the MEA concept, multiport converters could connect the whole EPDS while guaranteeing the galvanic isolation between buses. Since multiport converters would give rise to a completely different EPDS topology, dominated by power electronics interfaces, the stability of such a system must be assessed. This article investigates the input impedance of multiple active bridge (MAB) converters when interfaced with a single dc bus and multiple resistive loads. A transfer function-based input impedance model of the MAB converter is proposed. To validate the proposed input impedance model, the verification of input impedances of a triple active bridge (TAB) converter and a quadruple active bridge (QAB) converter is carried out using both simulation and experimental results.

Developing Capacity Reduction Factors for Curbside Bus Stops Under Heterogeneous Traffic Conditions

Traffic characteristics of a roadway are significantly influenced by bus stops, and it becomes more chaotic when a separate bus bay is not provided and the bus has to be stopped in the curb lane. The present study analyzes the effect of such bus stops on the midblock capacity of urban arterials under heterogeneous traffic conditions. Field data have been collected at six sections of six-lane divided urban arterial roads; out of that, three sections have not marked with bus stop and referred to as base sections, whereas the other three have designated bus stops and denoted as friction sections. A set of simultaneous equations are established using speed and flow data to estimate the midblock capacity of urban roads and found to be 6000 PCU/h for one direction of flow. Further, a set of simultaneous equations are developed between the speed of a vehicle type and the densities of all categories of vehicles with densities of stopped buses in their individual terms. These equations are solved for any number of stopping buses at a fixed proportion of vehicles in the traffic stream for different traffic volume levels and thus get the capacity curves. It has been found that the capacity of urban arterials is reduced by 6.6–28.3% when the frequency of stopping buses is as low as 20 bus/h to as high as 120 bus/h, respectively. The study outcomes are useful for designing bus stops and at the same time estimating the capacity of such sections in order to reduce the congestion on the urban roadway network.

Robust Speed-Sensorless Vector Control of Doubly Fed Induction Motor Drive Using Sliding Mode Rotor Flux Observer

This paper presents a robust observer for sensorless speed control of doubly fed induction motor (DFIM), based on the slidin mode. In the first step, a model of the doubly fed induction motor fed by two PWM inverters with separate DC bus link is developed. In the second step and in order to provide a robust separate control between flux and motor speed a vector control by field oriented strategy applying a sliding mode regulator was implemented. Finally, speed estimation of a doubly fed induction motor based on sliding mode observer is presented. The simulation tests schow the effectiveness of the proposed method especially in the load disturbances, the change of the refrence speed and low speed. Also the influence of parameter variations will be studied by simulation

Optimal Adjustment Schemes on the Long Through-Type Bus Lines considering the Urban Rail Transit Network

It is of great importance to optimize the schemes of long through-type bus lines to adapt to the urban rail transit network. Focusing on the long through-type bus lines close to metro stations, a bilevel programming model on the adjustment schemes of bus lines is proposed, taking the impacts of urban rail transit network into account. The upper level model aims at adjusting the setting decisions of stop stations and vehicle headways of bus lines to minimize the passenger travel cost and maximize the benefits of bus operators. The lower level model is a passenger flow assignment model based on Logit-SUE considering the crowding perception of passengers in bus vehicles. Moreover, the constraint of average load factor of the bus line sections is considered. Then the genetic algorithm is applied to solve the proposed model, and a numerical example is conducted to verify the effectiveness. Results show that the value of the objective function of the model is improved by 27.2%, in comparison with the original scheme. Even though the average travel cost of passengers increases slightly, the bus line operation cost and the imbalance degree of load factors are reduced by 46.1% and 18.6%, respectively. The sensitivity analyses show that it is better to divide the long through-type bus line into several separate bus lines with independent operation, respectively, under the condition of unbalanced passenger flow distribution. Meanwhile, the multiple bus lines are more adapted to the unbalanced passenger flow distribution when the weight of the benefits of the bus operators in the total objective function is bigger. Besides, the lower time value that the passengers perceive, the more passengers willing to take bus than metro trains. As the increment of the passenger time value, the combination of feeder bus lines and a longer bus line is better for passengers’ trip demand than the long through-type bus line.

An Algorithm for a No-Contact Digital Three-Phase Voltage Detector

Operating-lock systems are intended to prevent emergencies and injury-causing hazards at power substations. To arrange operating locks in switch and control gear (SCG) cells, it is necessary to have technical tools of no-voltage and voltage detection on conductor buses. The use of no-contact capacitance voltage detectors is an efficient way to make the installation process less labor-intensive. A matter of substantial interest is the design of a no-contact device able to indicate the absence or supply of voltage in each separate conductor bus and initiate phase rotation. The designed voltage detector uses a system of three capacitance electric- field detectors installed in the SCG opposite to the respective lines. Each of the detectors is affected by the fields generated by all the lines when energized. Thus, the output signal of each detector is the sum of partial signals conditioned by the voltage of each separate phase. Each of the three partial components in such signals is detected by digital signal processing. The operation of the detectors under uncertainty was modeled by the Monte Carlo technique in the MATLAB environment. Each imitative test with a random set of parameters results in vector responses from the detectors. The test results help draw diagrams on a complex plane for full-phase and open-phase modes. It is shown that the pertinence of signal vectors to a specific region makes it possible to unambiguously identify the absence or supply of voltage for each separate conductor bus.

A Case Study of Control and Improved Simplified Swarm Optimization for Economic Dispatch of a Stand-Alone Modular Microgrid

Due to the complex configuration and control framework, the conventional microgrid is not cost-effective for engineering applications with small or medium capacity. A stand-alone modular microgrid with separated AC bus and decentralized control strategy is proposed in this paper. Each module is a self-powered system, which consists of wind and solar power, a storage battery, load and three-port converter. The modules are interconnected by three-port converters to form the microgrid. Characteristics, operation principle, control of the modular microgrid and the three-port converter are analyzed in detail. Distributed storage batteries enable power exchanges among modules to enhance economic returns. Economic dispatch of the stand-alone modular microgrid is a mixed-integer programming problem. A day-ahead operation optimization model including fuel cost, battery operation cost, and power transmission cost is established. Because there are so many constraints, it is difficult to produce a feasible solution and even more difficult to have an improved solution. An improved simplified swarm optimization (iSSO) method is therefore proposed. The iSSO scheme designs the new update mechanism and survival of the fittest policy. The experimental results from the demonstration project on DongAo Island reflect the effectiveness of the stand-alone modular microgrid and the economic dispatch strategy based on the iSSO method.

Parallel RF Power Amplifiers Temperature Monitoring System Based on FPGA Device

The paper describes FPGA based temperature measurement system, for parallel monitoring of temperatures of the power semiconductors devices in RF power amplifiers. Proposed system allows for fast detection of the asymmetry in parallel RF power amplifier caused by failure of a single semiconductor power device like CMOS or MOSFET high power transistor. This information is important for evaluation of the system efficiency, current flow symmetry, and allowable output power in a given RF amplifier configuration. The article presents original concept of reading measurements from many 1-wire temperature sensors with minimal time delay between individual measurements thanks to digital temperature sensors operating on separate serial 1-Wire buses. FPGA device collects data from the temperature sensors and sends them through wireless interface to a remote terminal. The structure of the system as well as particular devices are described in the paper. The paper also presents selected results of practical experiments performed to confirm that the assumed concept of using an FPGA device to perform the high simultaneous readings from many sensors is feasible.

A Study on an Operation Strategy of Dual-Infeed HVDC System

This paper deals with the operation strategy of reactive power in a multi-infeed HVDC (MIHVDC) system, in which several converters are connected to the same or nearby separate AC buses. The potential problems concerning a MIHVDC system when feeding a weak AC network are as follows: the need for coordination of the recovery control, the possibility of voltage instability or low quality of the area connected to the MIHVDC system, and the risk of mutual commutation failures. These problems in MIHVDC systems are similar to those in single-infeed HVDC (SIHVDC) systems, but the differences with the phenomenon of the SIHVDC system are the interactions between converters. The main reason for the potential problems of HVDC systems (MIHVDC or SIHVDC) is voltage variation; therefore, to mitigate the voltage variations, the performances of the HVDC system should be enhanced. Consequently, to mitigate the potential problems of MIHVDC systems, several solutions are suggested in this study, including installing STATCOM and installing a line arrester on the tower. The study results will be applied to a multi-infeed HVDC system in Korea.