Hybrid Transmission Research Articles

Adaptive Robust Backstepping Control of the Speed Regulating Differential Mechanism for Wind Turbines

In this paper, a hybrid transmission system equipped with a speed regulating differential mechanism (SRDM) is proposed for grid-connected wind turbines (WTs) to generate constant-frequency electricity. However, the transmission system is subject to pulsating torque from disturbances in the power grid. Coupled with parameter uncertainties, the speed control accuracy of SRDM and the system stability can hardly be warranted by conventional adaptive or robust controllers. Aiming at the proposed WT, this paper presents a discontinuous projection-based adaptive robust backstepping controller (ARBC) with an extended state observer (ESO) for high-accuracy speed control of permanent magnet synchronous motor in SRDM. The designed control approach, whose global robustness is guaranteed by a feedback robust law, can effectively handle both parametric uncertainties and external disturbances together without using the large nonlinear feedback gain and violating any constraints during the transient period. Then, the desired tracking performances of ARBC with ESO are verified through comparative experiments in a built platform of the WT with SRDM. Comparative experimental results show that SRDM equipped with the integrated control method can accurately regulate the power frequency to constant under operating conditions of parametric uncertainties, varying wind speeds, subsynchronous resonance, and sudden load fluctuation in the power grid.

Robust optimisation of dynamic and NVH characteristics for compound power-split hybrid transmission

In this paper, vibro-acoustic characteristics of a power-split hybrid transmission including a compound planetary gear set are investigated by numerical procedure and refined system dynamics modelling. For validation of the numerical predictions, bench tests are performed for dynamic and acoustic responses of the hybrid transmission, contribution rates of acoustic radiation power induced due to the planetary gears, support bearings, transmission shafts and the gearbox housing are estimated. In improving the noise, vibration and harshness (NVH) performance of the transmission during hybrid vehicle acceleration, traction torques of the motors against the planetary gear parametric resonance are formulated and an optimal control strategy is proposed. By real road NVH test results acquired on board of the midsize hybrid car, it is demonstrated that a significant reduction of the planetary gear whine noise is achieved. As a result, numerical approaches applied to establish relationships between torques of the two traction motors and parametric excitations of the compound planetary gear train are experimentally validated.

A new technique for detection and classification of faults during power swing

The Lissajous figure of voltage and current signals of a transmission line follows a distinct pattern during power swing, although it deviates from its trend when a fault occurs. This feature of Lissajous figure is utilized in this article for detection and classification of faults during power swing. Autoregression technique is applied to obtain the trend of Lissajous figure and the deviation of actual Lissajous figure from this trend is calculated using Euclidean norm. Quarter-cycle moving window sum of Euclidean norm is used to obtain fault detection index for detection of faults during power swing. For identification of faulty phase, fault features are also calculated for three phases and ground using fault signals of only half-cycle duration after fault. The proposed method is tested on a hybrid transmission line consisting of an overhead line and an underground cable, simulated in electromagnetic transient program (EMTP). It can detect faults quickly and classify them with high accuracy irrespective of fault type, fault location, fault resistance, load angle, fault inception time and swing frequency. The method performs satisfactorily even under noisy condition upto 30 dB Gaussian noise. Finally, its performance is compared with one conventional and two novel methods to establish its efficacy.

Modeling and nonlinear parameter identification for hydraulic servo-systems with switching properties

Today’s automotive industry faces challenges in reducing emissions to comply with ever tightening statutory provisions. The future is set to provide cleaner vehicles which, on the one hand, reduce the required energy consumption while on the other hand are fit to fulfill customer preferences with regard to driving performance. As a result, the design and control of automotive components in the drive train are reconsidered. This paper treats the modeling and parameter identification of a hydraulic circuit for clutch actuation in automatic transmissions (AT) or dedicated hybrid transmissions (DHT). The examined hydraulic servo-system’s function is to provide the necessary pressure and volume flow for clutch actuation without usage of a hydraulic accumulator. Physical modeling and parameter identification is executed using testbed measurements of an according prototype hardware, aiming to contribute in finding a way towards destruction free identification of hydraulic systems. The nonlinear identification for the examined system that shows switching behaviour is performed using the derivation free particle swarm optimization (PSO) method. The physical models are developed for the purpose of being employed for the design of a trajectory tracking nonlinear model-based control scheme for clutch actuation based on the concept of input-output linearization.

A hybrid transmission scheme for networked control systems

Due to its obvious advantage on the efficient use of resources, the event-triggered mechanism is quickly applied in networked control systems (NCSs). However, when some event-triggered data packets are lost during network transmissions, it will become very challenging to analyse the NCSs since two consecutively event-triggered data are internally correlated and the relation will be destroyed when one of the data get lost. With the consideration, this paper proposes a hybrid communication mechanism for NCSs with data loss. Once a measurement that was event-triggered to be released got lost, the following measurements will be instantly transmitted to the controller. A networked controller is obtained for the NCS to guarantee the uniform ultimate boundedness of the system state. Finally, the validness and merits of the developed approach are illustrated through two well studied examples.

Research on AC/DC Power Flow Optimization by Using Interior Point Method

At present, China’s power system is developing in the direction of AC-DC parallel connection. AC-DC hybrid transmission has become the inevitable pattern of China’s future power grid. In the operation of AC/DC hybrid system, the optimization of multiple indexes is often considered. One of the economic problems of system operation is how to minimize the operation cost of the system. This requires the optimal solution of a system of nonlinear equations with constraints. Among the existing algorithms, the interior point method has excellent convergence performance and has been widely used in power system. In this paper, the basic principle of interior point method is introduced, and the interior point method is used to optimize the AC and DC power flow obtained. With the network operation cost as the objective optimization index. The Matlab software is used for programming and simulation calculation. On the basis of verifying the effectiveness of the algorithm, the algorithm is transplanted into the large network for calculation and analysis, and the adaptability of the test algorithm.

A New Location Method of Faulty Segment for Hybrid Transmission Lines Based on Transient Travelling Wave Analysis

The paper proposes a new location method of faulty segment for hybrid transmission lines combined with overhead line and cable. Conventional location method of faulty segment identify faulty segment through position calculation of fault point. However, affected by error, the fault at cable-overhead line joint is hard to be identified. In this approach, faulty segment is identified through characteristics comparison of transient travelling wave under different condition. Compared with situation that fault occurs on overhead line, if fault occurs in cable, there is an additional impedance discontinuity in cable. Thus, the amplitude and wave of various reflected wave will change significantly. The proposed method extracts various reflected waves based on time windows and polarity. It makes use of the relative amplitude and time difference between first travelling wave and secondary reflected wave of cable-overhead line joint as criterion of faulty segment location. To verify its effectiveness, fault simulations based on EMTDC are performed; the simulation results reveal that the proposed method can correctly identify the faulty segment for hybrid transmission lines.

Dynamic Modeling of Brake in Power-Split DHT and Pressure Tracking Control with Sliding Mode Variable Structure Method

Since the mode transition performance of power-split DHT (Dedicated Hybrid Transmission) are directly influenced by torque dynamic characteristic of the brake, the brake pressure should be controlled accurately. In this paper, a dynamic model of brake and its pressure regulating system are established by considering system nonlinear characteristics and input disturbances, and a sliding mode variable structure controller is developed to track the brake pressure. First, the operation principle of DHT’s pressure regulating system is introduced. Second, the dynamic models of solenoid proportional pressure valve, electromagnetic direction switching valve and brake are established with AMESim parametric plant model. Furthermore, a sliding mode variable structure controller for tracking pressure is designed based on MATLAB/Simulink. Finally, the AMESim parametric plant model is validated by measurements, and the proposed controller are verified by AMESim and Simulink co-simulation. The results show that the system dynamics can be well characterized by the AMESim parametric plant model. The target pressure can be tracked rapidly and accurately by using sliding mode variable structure controller and the controller has better robustness.

Toward Optimized Network Capacity in Emerging Integrated Terrestrial-Satellite Networks

In this paper, we investigate the transmission schemes of space data systems for optimized network capacity in an integrated terrestrial-satellite network (ITSN) with a two-layered space segment. First, a theoretical model of the network capacity is developed to evaluate the strategy of utilizing both direct and relayed transmissions. Second, we consider the ideal and the resource-constrained scenarios in which the corresponding network capacity is modeled with respect to the scheduling scheme. In particular, closed form and semi-closed form solutions to difficult integer programs are achieved via rigorous mathematical analysis. The proposed model is general for exploring the capacity of various satellite network deployments whose solutions have not been obtained in prior studies. Furthermore, we verify the potential capacity of the different transmission schemes based on the proposed solutions and prove that the system's network capacity can be significantly improved by the hybrid transmission scheme. The theoretical framework proposed in this paper is expected to provide constructive insights in the design for the future space segments of ITSNs.

Study on stability evaluation in multi-send hybrid AC/DC transmission system

Our country has shown the significant features of high voltage direct current (HVDC) including multi-infeed and multi-send. Compared to multi-infeed system, there are a lot of weakness in the multi-send system, such as the grid structure is single and weak, which makes the interaction between AC and DC to a greater extent affect the stability of the multi-send hybrid AC/DC transmission system. In order to evaluating the system strength in multi-send hybrid AC/DC transmission system, for the first time, this paper proposed the general formula and simplified formula for multi-send short-circuit ratio (MSSCR), which accounts for the coupling between multi-dc projects. Considering the control characteristics of rectifier in sending-side and combining the maximum power curve method, the criticality of MSSCR is proposed. Multi-send critical short-circuit ratio (MSCSCR) is deduced by the quasi steady-state equation of rectifier, to determine the multi-send system is strength enough or not. The proposal of MSSCR is of considerable significance for effectively evaluating the stability performance of the multi-send AC/DC hybrid transmission system, completing the short-circuit ratio theoretical system, and consolidating the short-circuit ratio index status.

Hybrid TCP/UDP-Based Enhanced HTTP Adaptive Streaming System With Multi-Homed Mobile Terminal

In this paper, we propose a hybrid Transmission Control Protocol (TCP)/User Datagram Protocol (UDP)-based enhanced HyperText Transfer Protocol (HTTP) adaptive streaming system for multi-homed mobile terminal over heterogeneous wireless networks. Unlike the existing HTTP adaptive streaming system, the proposed system can utilize both TCP and UDP to overcome the performance degradation problem of TCP and improve the energy efficiency. The proposed system handles the types of transport protocols, requested video quality, and amount of data received through each wireless network as control variables based on network conditions, buffer occupancy, and energy condition of mobile terminal. When UDP is selected, the proposed system employs Raptor code as a forward error correction scheme to support a reliable data delivery and adaptively chooses the proper Raptor code parameters such as symbol size and amount of redundant data, and requests redundant data from the server to reduce the overhead. The proposed system is fully implemented in an android-based mobile terminal and tested in real WiFi and Long-Term Evolution (LTE) networks. The experimental results show that the proposed system can achieve good energy efficiency while providing a seamless high-quality HTTP adaptive streaming service.

Transmit Power Minimization for Vector-Perturbation Based NOMA Systems: A Sub-Optimal Beamforming Approach

Non-orthogonal multiple access (NOMA) is one of the potential multiuser supporting techniques in the fifth generation (5G) cellular systems due to its higher spectrum efficiency (SE) and cell-edge throughput. Vector-perturbation (VP) is widely known as one of the nonlinear precoding schemes that achieves near-capacity performance in practical wireless multi-input-multi-output (MIMO) communication systems. In this paper, we propose a hybrid transmission strategy based on VP and NOMA (VP-NOMA) by designing a beamforming matrix with the power allocation strategy to minimize total transmit power for certain quality of service (QoS) requirements. Rather than searching for the optimal beamforming matrix, we propose a more intuitive sub-optimal algorithm, called iteration beamforming for VP-NOMA systems (IBVP-NOMA), to find beamforming vectors. Further, different user clustering strategies are considered and compared to enhance the performance of the VP-NOMA systems. The simulation results demonstrate that the proposed method requires lower transmit power than the NOMA system without VP.

Fast fault detection during power swing on a hybrid transmission line using WPT

This paper presents a new technique for very high speed detection of fault during power swing on a hybrid transmission line consisting of an overhead line and an underground cable. The wavelet packet transform with the mother wavelet db1 is utilised to segregate the high-frequency components from three-phase current signals recorded at the relay point and a fault detection index is calculated using these components to detect faults during power swing. The proposed method is tested on a 400 kV double circuit transmission system and a 400 kV 3-machine 9-bus Western System Coordinating Council system simulated in electromagnetic transient program software for both symmetrical and asymmetrical faults, different fault resistances, load angles, and fault inception times at random locations on the transmission line. Its performance is also analysed for close-in faults, high dc offset current, and the faults on the series compensated transmission line. The method is very fast to detect faults during power swing irrespective of the variations of fault conditions, and a comparative assessment with the existing methods justifies its merit.

Study on speed and torque control of a novel hydromechanical hybrid transmission system in wind turbine

A wind turbine is the most typical machine used to capture energy from the wind. The system design goal of a wind turbine is to obtain as much energy as possible from the wind while transmitting as much of that energy to the grid as possible, all under the highest possible level of stability. Currently, many inherent weaknesses result in a high failure rate in common commercial wind turbines with gear drive systems. To improve the performance, in this study, a typical 1.5 MW gear transmission was redesigned into a novel hydromechanical transmission system (HMTS). Parameters related to the HMTS efficiency were analysed to ensure that the efficiency was relatively high. The variable speed ratio (VSR) and torque triple absorption (TTA) principle were thoroughly deduced. Moreover, a MATLAB/Simulink- AMESim cosimulation model was proposed, and a 30 kW proportional prototype was established. Both simulation and experimental results show that the structural design and proposed control strategies meet the design goals, including a relatively high transmission efficiency around the rated wind speed, speed control below the rated wind speed, and torque control above the rated wind speed. These achievements should guarantee the future application of the novel transmission system in wind turbines.

Automatic Enumeration of Feasible Configuration for the Dedicated Hybrid Transmission With Multi-Degree-of-Freedom and Multiplanetary Gear Set

This paper presents a novel design approach to systematically synthesize available configurations for dedicated hybrid transmission (DHT) systems subject to design constraints and required operation modes by using simple planetary gear sets (PGSs). The configuration synthesis process includes two main steps. The first step is the synthesis of the PGSs by synthesizing all the components to a simple PGS subject to the design constraints. The second step is to combine the structural and shift elements into all configurations and detect those meeting the requirements with the mechanical and operation mode constraints. By applying the proposed design approach, the configurations of the Toyota’s hybrid systems (THSs) and Voltec-II prove the feasibility of the method. Furthermore, several new DHT configurations are synthesized under the new design conditions. The proposed design approach is capable of systematically synthesizing new DHT systems with multiple PGSs, variable design constraints, and expected modes.

A fault locating method for multi-branch hybrid transmission lines in wind farm based on redundancy parameter estimation

In order to solve the problem of “abandoned” wind caused by short circuit faults in a wind farm, a wind farm fault locating method based on redundancy parameter estimation is proposed. Using the characteristics of the traveling wave, transmission equations containing the position of the fault point are constructed. Parameter estimation from statistical theory is used to solve the redundant transmission equations formed by multiple measuring points to locate the faults. In addition, the bad data error detection capability of the parameter estimation is used to determine bad data and remove them. This improves locating accuracy. A length coefficient is introduced to solve the error enlargement problem caused by a transmission line sag. The proposed fault locating method can solve the fault branch misjudgment problem caused by the short circuit faults near the data measuring nodes of the wind farm based on the proposed fault interval criterion. It also avoids the requirements to the traveling wave speed of traditional methods, thus its fault location is more accurate. Its effectiveness is verified through simulations in PSCAD/EMTDC, and the results shows that it can be used in the fault locating of hybrid transmission lines.

Nanoindentation Properties and Finite Element Analysis of the Rostrum of Cyrtotrachelus buqueti Guer (Coleoptera: Curculionidae).

This work focuses on the application of nanoindentation measurements and the finite element method for analyzing the mechanical properties of the rostrum of the outstanding driller Cyrtotrachelus buqueti Guer. Nanoindentation tests were carried out to measure the Young's modulus and hardness of the rostrum, with the results for the "dry" samples being 13.886 ± 0.75 and 0.368 ± 0.0445 GPa, respectively. The values for the "fresh" samples showed no clear difference from those of the "dry" ones. Moreover, field observation was conducted to determine the motion behaviors of the rostrum on the weevil. Micro-computed tomography technology was employed to obtain structural information about the rostrum, using 9 µm slices. A real three-dimensional model of the rostrum was created using the MIMICS application. Finally, the mechanical properties of the rostrum were determined by finite element analysis. It was concluded that the rostrum provides an ideal biological template for the design of biocomposite materials and lightweight tube-shaped structures. The properties determined in this study can potentially be applied in different fields, such as in the design of automotive hybrid transmission shafts, helicopter tail drive shafts, robotic arms, and other sandwich structures in aerospace engineering.

Evaluation of transmission losses of various Dedicated Hybrid Transmission (DHT) with a lossmap-based simulation model

This paper presents a simulation methodology developed at the Institute of Automotive Engineering (IAE). With this simulation method, transmission lossmaps can be calculated for Dedicated Hybrid Transmission (DHT). These transmission lossmaps are considered within the control strategy section of a modular simulation model, which can lead to more realistic simulation results. Four DHT concepts are investigated using this simulation methodology: three multi-mode DHT (MM-DHT) transmission concepts and a Power Split DHT (PS-DHT) concept. All concepts have two electric machines (EM). The first concept is a MM-DHT, which was developed with the transmission synthesis of the IAE. This DHT concept has two planetary gear sets (PGS), four shifting elements, and two EM. The other MM-DHT concepts are based on the Voltec 2 and the CT6. They also have two EM. The Voltec 2 has two PGS and three shifting elements. The CT6 has three PGS and five shifting elements. The power split DHT has one PGS and no shifting elements. For the evaluation of the transmission concepts, consistent and representative performance requirements are first defined, which must be fulfilled by all concepts. Afterwards, the transmission losses of the individual concepts can be subdivided via the lossmap-based simulation model for the different loss components. Finally, the DHT concepts are examined and evaluated with regard to mechanical efficiency and fuel consumption in the WLTC.

Investigation of the power losses of the hybrid transmission DE-REX based on modeling and measurement

Electric and hybrid powertrains are developed to reduce the energy and fuel consumption of vehicles. Recently, multi-speed transmission systems were discussed for further reduction of the energy consumption of electric vehicles. Therefore, analyzing the power losses of such transmissions is of interest. In this paper, the novel powertrain concept DE-REX (Two-Drive-Transmission with Range-Extender) and the experimental investigation of its overall power losses is first introduced. A method is then developed to model and analyze the power losses of this hybrid transmission based on experimental data. After the validation of the method, the overall power loss model is eventually applied to estimate the power losses of the transmission at other driving modes, which were not measured on the test rig. The method is used to understand the characteristics of power losses inside the transmission in a hybrid powertrain and to optimize powertrain power losses in future.

A generic transmission model for hybrid electric drives

The design problem of hybrid electric drivetrains has a large design space, especially, when complex dedicated hybrid transmissions that combine an internal combustion engine with multiple electric machines are considered. To evaluate a drivetrain design over a driving cycle, a transmission model is needed. To avoid the need of modeling every drivetrain concept individually, a generic transmission model for hybrid electric drives is developed. The developed model integrates the dynamic behavior of all conventional-, electric-, and hybrid- transmission mode types. Mode types and mode type dependent control variables are defined. The outputs of the model are the torque and rotational speed of all power sources of the drivetrain. The inputs of the model are the torque and speed of the wheels, and the control variables. As a practical example, the model is used to compare the energy efficiency of two complex dedicated hybrid transmissions by optimizing the control for both over a driving cycle.