Search

The use of series architecture nowadays is mainly on hybrid buses. In comparison with series-parallel and parallel architectures, which are usually exploited on medium-size cars, the series architecture allows achieving internal combustion engine higher efficiency. The downside of this architecture, due to a double energy conversion (i.e., mechanical energy converted in electrical energy and electrical energy converted again in mechanical energy), is that additional losses are introduced. For this reason, the parallel and the series/parallel architectures were considered more suitable for hybrid medium-size cars. Nevertheless, the use of new technologies can change this scenario. Regarding storage systems, supercapacitors achieved a significant energy density, and they guarantee much higher efficiency than battery storage. Moreover, the use of wide-bandgap components for power electronic converters, such as silicon carbide devices, assure lower losses. In this scenario, the series architecture can become competitive on medium-size cars. This paper shows a review of various studies performed on this topic.

Nowadays HVDC based on Voltage Source Converters (VSC) are based on the Modular Multilevel Converter (MMC) and the applications in which the Full Bridge (FB) Cells are used are increasing. Therefore, this paper presents an analytical study of the MMC interaction between the converter currents and voltages. The study is applied to the case of the FB Cell based MMC, with special attention to the capacitor voltage ripple caused by this interaction.

In this paper, a novel approach to determine the model of an ICNL (Independently Controlled Neutral Leg) is proposed. Based on this model, a cascaded control method is developed to provide a steady neutral point connection for a three-phase four-wire inverter and to balance the two DC capacitors voltages of a split DC-bus. Validation of the model is realised by simulations and the control has been tested by experiments. Results have shown good performance even with a high level of neutral current, which demonstrate the ability of the system to work within an unbalanced load or grid.

Sensorless algorithms for Permanent Magnet Synchronous Motors (PMSM) have achieved increasing interest in the technical literature over the last few years. They can be divided into active methods and passive methods: the first inject high-frequency signals exploiting rotor anisotropy, whereas the second are based on observers. Recently, a sensorless control based on a rotor flux observer has been presented in the technical literature, which gives very accurate results in terms of rotor position estimation and robustness. In this paper, the aforementioned observer is considered and a procedure for choosing stabilizing gains of the observer is proposed. The contribution of the paper is three-fold: the mathematical modelling of the rotor flux observer, the methodology for the definition of the observer gains, and the presentation of the experimental results.

Induction machines are always the most used machines in industry, due to the several advantages they offer. The quite simple V/Hz control strategy is one of the most commonly used strategies to control induction motors speed, due to its simplicity and ease of implementation. However, using this strategy for controlling high power induction motors may cause instability in some regions, leading to high oscillations in currents and in motor torque. Therefore, the authors propose an improved version of the V/Hz control strategy, which compensates for these oscillations by correcting the speed reference using the stator current. The results obtained are presented, showing excellent results in compensating for these oscillations in motor currents and torque.

The modulation strategy, proposed in the technical literature to control the three-switch double-input bidirectional DC-DC converter, forces the converter itself to work in Continuous Conduction Mode at low-load and therefore efficiency drops significantly. In this paper, a novel modulation strategy, exploiting Discontinuous Conduction Mode at low-load, is proposed. Converter efficiency increase is evaluated with simulations in MATLAB/Simulink Plecs environment. Finally, the control is validated with experimental tests.

The Modular Multilevel Converter (MMC) concept is a modern energy conversion structure that stands out for a number of interesting features that opens wide application chances in Power Systems, for example for efficient grid integration of renewable sources. In these high-voltage, high-power application fields, a high efficiency is mandatory. In this regard, an interesting and promising development opportunity could be to make soft-switching the elementary converters of the submodules (cells), half H-bridges or full H-bridges, obtaining at the same time the advantage of increasing the switching frequency. The-Active Resonant Commutated Pole Converter (ARCP) or the Auxiliary Quasi Resonant DC-link Inverter (AQRDCL) soft-switching topologies appear adequate for this purpose. This paper is dedicated to examining these development possibilities.

The large boom in the Hybrid Electric Vehicle (HEV) market sector has seen the spread of three main powertrain configurations: Discontinuously Variable Transmission (DVT) parallel architectures, Continuously Variable Transmission (CVT) parallel architectures and series architectures. In particular, CVT powertrains can count the highest number of sales in the HEV industry. In spite of this fact, in depth electrical losses analysis of this configuration and the introduction of more efficient electric component question the adoption of this powertrain as the model of energy efficiency. This paper aims to summarize the main results available in the scientific literature on this topic. It is firstly shown a fuel consumption comparison between the two parallel powertrains, secondly a brief description of the main electric component innovations is reported in order to fully understand the effects they have on the series architectures. Lastly, a fuel consumption comparison between the most efficient parallel solution and the series architecture is shown for the purpose of identifying the most efficient powertrain architecture.

In this paper, starting from the measurements available for a 2000 cm3 turbocharged diesel engine, an analytical model of the turbocharger is proposed and validated. The model is then used to extrapolate the efficiency of a power unit with a diesel engine combined with a turbocompound system. The obtained efficiency map is used to evaluate the fuel economy of a supercapacitor-based series hybrid vehicle equipped with the turbocompound power unit. The turbocompound model, in accordance with the studies available in the technical literature, shows that the advantages (in terms of efficiency increase) are significant at high loads. For this reason, turbocompound introduction allows a significant efficiency improvement in a series hybrid vehicle, where the engine always works at high-load. The fuel economy of the proposed vehicle is compared with other hybrid and conventional vehicle configurations.

A double-input DC-DC converter is taken into account in this paper. The converter is bidirectional and both currents can be controlled independently. On the one hand it allows to reduce the number of switches, on the other hand, it exhibits a higher efficiency in comparison to a traditional solution with two half-bridge converters in parallel connection. However, the control strategy proposed in the technical literature forces the converter to work in Continuous Conduction Mode at low-load, which leads to a low conversion efficiency. In this paper, a novel control, which exploits Discontinuous Conduction Mode, is presented. Efficiency increase is evaluated with a thermal model in MATLAB/Simulink Plecs environment and the control algorithm is then validated with experimental tests on a converter prototype.

A self-commissioning sensorless algorithm for surface mounted permanent magnet synchronous motors is shown in this paper. The sensorless method is based on rotor flux observer and, differently from methods based on motor anisotropy, it does not require high frequency voltage injection; therefore, it does not cause additional losses and acoustic noise. The aim of this paper is to evaluate sensorless behavior in the low speed region, where performance of methods without high frequency voltage injection generally worsen. In particular, motor starting with rated torque at standstill and with intermittent torque is analyzed. Regarding self-commissioning algorithm, the estimation of motor parameters becomes crucial if this algorithm is used together with sensorless control, since the estimated values not only are used to realize the motion control (e.g., field oriented control) but also to estimate rotor position. Sensorless algorithm sensitiveness to motor parameter uncertainties is investigated. Experimental results are shown, using four different motors of various sizing.

One of the most important innovation expectation in railway electrical equipment is the replacement of the on-board transformer with a high power converter. Since the transformer operates at line-frequency (i.e., 50 Hz or 16 2/3 Hz), it represents a critical component from weight point of view and, moreover, it is characterized by quite poor efficiency. High power converters for this application are characterized by a medium frequency inductive coupling and are commonly referred as Power Electronic Transformers (PET), Medium Frequency Topologies or Solid-State Transformers (SST). Many studies were carried out and various prototypes were realized until now, however, the realization of such a system has some difficulties, mainly related to the high input voltage (i.e., 25 kV for 50 Hz lines and 15 kV for 16 2/3 Hz lines) and the limited performance of available power electronic switches. The aim of this study is to present a survey on the main solutions proposed in the technical literature and, analyzing pros and cons of these studies, to introduce new possible circuit topologies for this application.

The large-scale spread of hybrid electric vehicles (HEVs) in the automotive industry is dominated today by continuous variable transmission parallel powertrain as far as medium size car are concerned. As a matter of fact, the tendency in this sector is to design parallel architectures in that they have provided until now a higher overall powertrain efficiency. However, technological improvements in many electric components and their increased efficiency can reshape this vision and give new outlines on HEV structure design. This paper aims to show the potentials of the series architecture, thanks to the latest electrical improvements especially in storage systems and power electronics. In particular, simulation models and fuel consumption data over different road missions are presented for the series architecture proposed in this study. In addition, a comparison between these results and data available in the scientific literature for state-of-the-art HEVs is reported.

In this paper an exhaustive study on the effects of the circulating currents in the modular multilevel converter in HVDC applications is presented. In the first part, an analytical study of the converter is reported, with emphasis on the capacitors voltage ripple in presence of different circulating currents. In particular, the effects of the second and fourth harmonic components in the circulating current are evaluated in a general working point and, in particular, in the more significant working points corresponding to the inverter, rectifier, inductive and capacitive operation modes. The second part is a simulated HVDC plant verification of the voltage capacitor ripple expression.

High switching frequency employed in modern power electronic converters is cause of important common mode electrical quantities, having as consequences the premature motor failure and other unwanted effects in drive systems. A new SVM scheme for cascaded multilevel converter, aimed to the attenuation of these consequences, is proposed.

Permanent magnet synchronous motor sensorless algorithms for low speed region are usually based on rotor anisotropy. Although many studies showed a good behavior of this type of control, high frequency voltage injection is required, which causes loud acoustic noise in addition to electrical losses. On the other hand, methods based on back electromotive force or rotor flux observer, which guarantee high performance in the medium–high speed region, do not required voltage injection. In this paper, a rotor flux observer based algorithm performance is analyzed, in order to extend its use also in the low speed region. Behavior both with no-load, linear torque, quadratic torque, constant torque and compressor-load torque is tested, especially focusing on motor starting. Improvements to rotor flux observer algorithms available in the scientific literature are discussed and their effectiveness is verified by experimental results.

A great boom of hybrid vehicles has taken place on the automotive market in recent years, in particular, all these vehicles are now equipped with a continuously variable transmission (CVT) thanks to the use of a planetary gear train and two electric motor-generators. The benefit provided by this system is the possibility to optimally control the engine velocity from an energy standpoint; in addition, drive comfort is increased thanks to the continuously variable transmission. However, this is obtained at the cost of some amount of electrical losses in the components necessary to realize the above-mentioned structure. This paper aims to evaluate the overall efficiency of this particular power train on different road missions; the same missions will be simulated at the same time for an identical hybrid vehicle equipped with a conventional transmission system. In order to perform an energy analysis of the two architectures, one has to accurately address the main components generating energy losses: it will be thus presented the set of equations from which the mathematical stationary model of the CVT was obtained and how the different electric components and the internal combustion engine were modeled. In addition, a brief description on the CVT optimization logic will be reported, the validity of this process will be then confirmed by comparing the ICE working points deriving from it and those declared by Toyota. Finally, the fuel economy values coming from various road simulations will be compared in order to determine if or which hybrid architecture proves to be the most efficient one.

This paper presents dynamic characterization and control of an upper-limb rehabilitation machine aimed at improving robot performance in the interaction with the patient. An integrated approach between mechanics and control is the key issue of the paper for the development of a robotic machine with desirable dynamic properties. Robot inertial and acceleration properties are studied in the workspace via a graphical representation based on ellipses. Robot friction is experimentally retrieved by means of a parametric identification procedure. A current-based impedance control is developed in order to compensate for friction and enhance control performance in the interaction with the patient by means of force feedback, without increasing system inertia. To this end, servo-amplifier motor currents are monitored to provide force feedback in the interaction, thus avoiding the need for force sensors mounted at the robot end-effector. Current-based impedance control is implemented on the robot; experimental results in free space as well as in constrained space are provided.