Impact of optical current transformer on protection scheme of hybrid transmission line

Continuity of power transmission is important to ensure the reliability of the electricity supply. As most system faults are temporary, the auto reclose (AR) scheme has been used extensively to minimise the outage duration, prevent widespread outages, thus increase system stability. Meanwhile, the hybrid transmission line (HTL) combining overhead line (OHL) and high voltage cable has been introduced to provide an inexpensive solution for an urban power grid. Protecting HTL with a conventional protection system would forbid the operation of the AR scheme due to difficulty to ensure whether the fault occurred on the OHL or cable section. Therefore, the circulating current protection (CCP) scheme is used in the cable section to ensure the fault location and block the AR scheme. The technology of an optical current transformer (OCT) as one of the non-conventional instrument transformers (NCIT) has emerged to provide a solution to drawbacks on the conventional current transformer (CCT). Consequently, this paper investigated the impact of using OCT over the CCT for CCP of the HTL. The result shows that OCT could be used for CCP on much longer cable sections thus increase its reliability as the AR scheme can be used on longer or multiple cable section.

Design of Gerotor Pump and Influence on Oil Supply System for Hybrid Transmission

Electric continuously variable transmission (E-CVT) is a vital part of the automobile in order to enhance the power coupling. The oil pump is an important power source component in the hybrid transmission system. Its efficiency exerts a significant impact on the efficiency of the oil supply system and even the hybrid transmission system. In this study, a gerotor pump is designed in line with the requirements of a certain type of hybrid electric vehicle. A Non-dominated Sorting Genetic Algorithm II (NSGA-II) genetic algorithm was employed to optimize the rotor tooth profile. The proportional-derivative (PD) control of the oil supply system was realized to lower the functional error of the oil supply system based on the AMESim simulation platform. In addition, the prototype test was performed to verify the rationality of the design.

Two-terminal fault detection and location for hybrid transmission circuit

This paper presents the algorithms developed to detect and locate the faults ata hybrid circuit. First, the fault detection algorithm was developed using the comparison of total positive-sequence fault current between pre-fault and fault times to detect the occurrence of a fault. Then, the voltage check method was used to decide whether the fault occurred at overhead line (OHL) or cable section. Finally, the fault location algorithm using the impedance-based method and negative-sequence measurements from both terminals of the circuit were used to estimate the fault point from local terminal. From the tests of various fault conditions including different fault types, fault resistance and fault locations, the proposed method successfully detected all fault cases at around 1 cycle from fault initiation and with correct faulted section identification. Besides that, the fault location algorithm also has very accurate results of fault estimation with average error less than 1 km and 1%.<br /><div> </div>

Impact of cost-optimized dedicated hybrid transmission (DHT) constraints on powertrain optimal control

In the transition from internal combustion engines (ICE) based vehicles to pure battery electric vehicles (BEVs), the powertrain is becoming increasingly electrified (xEV). Based on their capability to recuperate brake energy in the legislative test cycles, intermediate xEV vehicles are classified as mild and strong electrified vehicles. Growing xEV sales currently pave the way for the application of cost-optimized dedicated components. The B segment vehicle analyzed in this work is currently equipped with a conventional coaxial transmission, which can offer multiple power sources (combustion engine, electric machine, or hybrid) in a single shift with an additional clutch. A cost-optimized dedicated hybrid transmission (DHT) is designed by eliminating the launch clutch, synchronizers, and redundant energy travel paths to replace the coaxial transmission. The DHT requires one shift for each energy path to connect the power source to the wheels. The flexible coaxial transmission requires only a low specific number of gear shifts to drive a typical test cycle. However, the DHT has constrained energy paths, leading to a high specific number of gear shifts to drive identical test cycles when applied with the standard Adaptive Equivalent Consumption Minimization Strategy (A-ECMS) optimal control. A one dimensional closed-loop simulation model for the passenger car longitudinal dynamics is used in this analysis. The vehicle velocity and evaluation criteria for the simulation are based on the Worldwide harmonized Light vehicles Test Procedure (WLTP). The loss maps from steady-state test bench measurements for the internal combustion engine (ICE), the electric motor (EM), and the transmission unit are used as inputs in building the simulation model. A drivability penalty approach is introduced in the standard A-ECMS optimal control to reduce the number of gear shifts. The work analyzes the gear shift behavior and the absolute CO2 emission between the cost-optimized DHT and the existing coaxial transmission for the considered vehicle application. Detailed power flow using a Sankey diagram from different onboard vehicle sources for the cost-optimized DHT solution is included in the results section. The developed model is validated with a prototype vehicle environment on the Urban Dynamometer Driving Schedule (UDDS).