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The energy management strategy (EMS) or power management strategy (PMS) unit is the core of power sharing control in the hybridization of automotive drivetrains in hybrid electric vehicles (HEVs). Once a new topology and its corresponding EMS are virtually designed, they require undertaking different stages of experimental verifications toward guaranteeing their real-world applicability. The present paper focuses on a new and less-extensively studied topology of such vehicles, HEVs equipped with an electrical variable transmission (EVT) and assessed the controllability validation through hardware-in-the-loop (HiL) implementations versus model-in-the-loop (MiL) simulations. To this end, first, the corresponding modeling of the vehicle components in the presence of optimized control strategies were performed to obtain the MiL simulation results. Subsequently, an innovative versatile HiL test bench including real prototyped components of the topology was introduced and the corresponding experimental implementations were performed. The results obtained from the MiL and HiL examinations were analyzed and statistically compared for a full input driving cycle. The verification results indicate robust and accurate actuation of the components using the applied EMSs under real-time test conditions. [ABSTRACT FROM AUTHOR]

This paper describes how an electrical variable transmission (EVT) can be used as an alternative for mechanical continuously variable transmission (CVT) systems. An EVT is an electromagnetic power split device having two mechanical and two electrical ports. The speed ratio between both mechanical ports (rotors) can be varied in a continuously variable way, so that this machine can be used as an electromagnetic alternative for the mechanical push-belt and half-toroidal CVT. Its operating principle is based on splitting the power into an electromagnetic direct path and an electrical path involving two inverters connected back to back. Its potential use as a CVT is investigated by comparing experimental data against toroidal and belt CVT data from literature having comparable power ratings. To this end, measurements are performed on a prototype \text120-kW permanent magnet EVT. [ABSTRACT FROM AUTHOR]

A novel dual power flow (DPF) wind energy conversion system (WECS) based on an electrical variable transmission (EVT) machine is proposed recently. The structure of the novel EVT-based WECS, especially the grid-connected configuration, is different from any other existing WECSs. In this paper, the grid-connected control strategies of the DPF- WECS are proposed by controlling the DC-link and the inner rotor side converter, where the DC-link with and without the energy storage system (ESS) is considered separately. The relevant control strategies are presented to enhance the grid fault ride through capability of the DPF-WECS. Moreover, the maximum power point tracking control strategy and the pitch control strategy are also studied to implement the complete functionality of the DPF-WECS. The simulation model of the DPF-WECS is developed based on the EVT mathematical models and proposed control strategies. Finally, the simulation results verify the efficiency of the proposed control strategies for the DPF-WECS. [ABSTRACT FROM AUTHOR]

An electrical variable transmission (EVT) is an electromagnetic power-split device with two mechanical and two electrical ports. It can be used in hybrid electric vehicles to split the power to the wheels in a part coming from the combustion engine and a part exchanged with the battery. Although crucial for the EVT design and evaluation, no papers are found to give a detailed overview of the different loss components in such a machine and how they can be calculated and measured. In contrast to conventional electrical machines, this machine has more degrees of freedom, which can be exploited to measure the different loss contributions separately. This paper proposes a methodology to identify and measure the different loss components in this kind of machines. The proposed method is able to identify the iron losses in stator and inner rotor, the copper losses, bearing losses, and slip ring friction losses separately. To this end, measurements of both torque and speed sensors in different operating points are combined. The methods are applied to identify the different loss contributions in a prototype permanent magnet assisted EVT, both in no-load operation as under load where its functionality as power-split device is evaluated. [ABSTRACT FROM PUBLISHER]

The dual power flow wind energy conversion system (DPF-WECS) is a novel system which is based on the electrical variable transmission (EVT) machine. The proposed sensorless control for the DPF-WECS is based on the model reference adaptive system (MRAS) observer by combining the sliding mode (SM) theory. The SM-MRAS observer is on account of the calculations without the requirement of the proportional-integral (PI) loop which exists in the classical MRAS observer. Firstly, the sensorless algorithm is applied in the maximum power point tracking (MPPT) control considering the torque loss for the outer rotor of the EVT. Secondly, the sensorless control is adopted for the inner rotor control of the EVT machine. The proposed sensorless control method based on the SM-MRAS for the DPF-WECS is verified by the simulation and experimental results. [ABSTRACT FROM AUTHOR]

An electrical variable transmission (EVT) can be used as a power splitting device in hybrid electrical vehicles. The EVT analyzed in this paper is a rotating field electrical machine having two concentric rotors. On the outer rotor, permanent magnets (PMs) are combined with a dc-field winding, being the first implementation of its kind. The magnetic field in the machine as well as the electromagnetic torque on both rotors are a function of the q- and d-axis currents of the stator and inner rotor, as well as the dc-field current. To describe and fully understand this multiple-input multiple-output machine, this paper gives an overview of the influence of the different current inputs on the flux linkage and torque on both rotors. Focus is given to the hybrid excitation in the d-axis by combining the dc-field current and the alternating currents. This has the advantage compared to other EVT topologies that unwanted stator torque can be avoided without stator d-axis current flux weakening. Results of the analysis are presented by means of the torque to current characteristics of a double rotor PM-assisted EVT, as well as the torque to current ratios. The machine characteristics are finally experimentally verified on a prototype machine. [ABSTRACT FROM PUBLISHER]

A way to improve existing hybrid vehicles is by globally optimizing the design of their components in relation to their actual use. This paper proposes a global optimal design method for power-split hybrid electric vehicles (PS-HEVs) equipped with an electric variable transmission (EVT). A genetic algorithm is used to optimize system parameters. The process includes discrete dynamic programming (DDP) for optimal energy management. The optimization focuses on minimizing fuel consumption and the number of battery cells. Pareto fronts are depicted and compared for different drive cycles, and they show the existence of a possible tradeoff between fuel consumption and battery size. [ABSTRACT FROM AUTHOR]

Automotive engineers and researchers have proposed different topologies for series–parallel hybrid electric vehicles (SP-HEVs). The Toyota Hybrid System (THS) is the best known SP-HEV-based vehicle, but alternative solutions, such as electric variable transmission (EVT), have been also proposed. An efficient comparison between these different solutions is a key point to estimate the added value of each topology. This paper presents the application of optimal control to two series–parallel hybrid architectures for efficiency assessment purposes. The dynamic programming method is applied to the THS and to a virtual hybrid vehicle with an EVT. The way to take into account the supplementary degree of freedom provided by the decoupling of the wheels and the engine in both topologies is presented. The optimal fuel consumption is then compared on different driving cycles and brings out an overconsumption of the EVT topology. Then, a parametric study shows that inserting an appropriate gear ratio on the internal-combustion-engine (ICE) shaft can improve the EVT efficiency that becomes close to the THS efficiency. [ABSTRACT FROM PUBLISHER]

This paper focuses on the control for the dual power flow wind energy conversion system (DPF-WECS) based on the permanent magnet electrical variable transmission (PM-EVT) machine. The PM-EVT machine can be considered as two permanent magnet synchronous machines (PMSMs) by ignoring the magnetic field coupling between the inner rotor and stator windings. For the DPF-WECS, the speed of the inner rotor should be controlled precisely to generate the constant voltage and constant frequency electricity. However, the rotor position of the inner PMSM composed of the inner rotor and outer rotor is difficult to be measured exactly due to the rotational stator and rotor. Thus the inner PMSM is hardly to be controlled using vector control strategy with the measured rotor position. In this paper, a sensorless control strategy based on the model reference adaptive system (MRAS) for the PM-EVT machines with double layer permanent magnet outer rotor for the DPF-WECS is proposed and evaluated by simulation. The effectiveness of proposed control strategy is verified by experimental results. [ABSTRACT FROM AUTHOR]

In the widely applied non-direct-driven wind power generation system, a gearbox is connected between the wind turbine and high-speed doubly fed induction generator so that the system can supply power with constant voltage and constant frequency as the wind turbine speed varies. However, the multilevel mechanical gearbox is rather vulnerable and poses many difficulties to maintain. Electrical variable transmission (EVT), an electrical continuous variable gearbox, is a very competitive alternative for the vulnerable constant speed-ratio mechanical gearbox. In this paper, the application of this machine in wind power generation system with its operational modes and control strategy is presented. The working principle of the EVT-based system is introduced, and the unique power conversion characteristics are investigated. A control algorithm with maximum power point tracking for the outer rotor is developed and implemented in a prototype machine. Both computer simulation and experimental results verify the working principle and the unique features of the EVT-based wind power generation system. [ABSTRACT FROM PUBLISHER]

This paper describes the mathematical modeling, analysis, and simulation results of a novel electrical variable transmission (EVT) for a series–parallel hybrid electric vehicle (SPHEV). The proposed EVT uses a two-degree-of-freedom (2-DOF) planetary gearset with four clutches to combine an engine and two electric machines with the vehicle. The topology of the planetary gearset is the same as that of conventional four-speed automatic transmissions. Therefore, the proposed EVT can be mass-produced and quite easily packaged. Nine operation modes can be realized. The properly arranged clutches more flexibly transmit power flow and avoid high spin losses for the engine and electric machines. Simulation under the New European Driving Cycle (NEDC) drive cycle shows that the fuel consumption of the proposed SPHEV is 5.62% lower than a benchmark vehicle, which uses two planetary gearsets and no clutches, indicating the fuel economy potential of this concept. The life cycle of the electric machines is expected to be extended, because the open or locked operations of the clutches allow efficient operation and, thus, might reduce the chance of overheating. Finally, the speed range of the electric machines is found to be smaller, compared with that used in the benchmark vehicle, which implies ease of manufacture, good sustainability, and low cost. [ABSTRACT FROM PUBLISHER]