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The basic direct torque control (DTC) principle is to rotate the flux linkage forward, if the torque must be increased, and reverse, if the forque must be decreased. The torque is, however, increased only up to a maximum torque of the machine, which corresponds to a load angle of about 90[degrees] in a synchronous machine. This paper presents a method to overcome the possible loss of synchronism when using DTC. This requires either that the rotor angle is measured or estimated. Both of these cases are considered. Simulation and laboratory results are presented to show the effectiveness of the presented method. Index Terms--Estimation, rotating machine stability, synchronous motor drives.

Active magnetic bearings (AMBs) provide reliable solution for high-speed rotors, where oil-free and reliable operation are crucial. In high-power applications benefits of AMBs, compared to traditional rolling element bearings or fluid film bearings, are highly valued. Typical AMB rotors comprise two radial AMBs, which are designed with compressor or generator wheels integrated on the rotor. AMB dimensions and locations are carefully selected for each new application. The system design is being iterated such that the nodes of the lowest frequency rotor bending modes are sufficiently far away from the AMB and sensor nodes to ensure robust AMB control. The design is very challenging and cost sensitive. This work focuses on electromagnetic design, modeling, and control of fully levitated AMB-rotor with three radial AMBs. The additional bearing ensures that the same design can be reused with different applications and regardless of the changes in locations of nodes of the first bending mode. The control plant is modeled based on flexible rotor dynamics; while bearing inductances and forces are modeled with 2-D and 3-D finite element method (FEM) electromagnetic simulations. The presented multi-input multi-output (MIMO) model-based control is coupled and centralized with three actuator-sensor pairs for radial suspension. The control design is verified in simulations using nonlinear engineering models. Additionally, experimental identification results are included. [ABSTRACT FROM AUTHOR]

The article addresses coupled loss and thermal analyses of a bearingless drive with an operating speed range of 17 000–32 000 rpm. The drive is a part of a high-temperature heat pump system integrated in a high-speed compressor. This drive system comprises two bearingless motor units and an axial active magnetic bearing. The drive can be positioned horizontally or vertically. The positioning is directly related to the force necessary to raise and suspend the rotor. Furthermore, the amplitude of the suspension current has a significant effect on the motor winding and iron losses. The iron losses, eddy current losses in the magnets, and losses in the bandage are investigated by three-dimensional (3-D) and 2-D finite-element analysis. The influence of segmentation of the magnets on losses is analyzed. Friction losses of the coolant are calculated analytically, and all the losses obtained from the electromagnetic analysis are represented as distributed heat sources and coupled with the 3-D thermal field analysis. The temperature fields are modeled under different motoring and suspension current conditions and evaluated for horizontal and vertical positions of the motor. As a precaution, demagnetization of the magnets is also considered. [ABSTRACT FROM AUTHOR]

High-speed solid-rotor induction machines (HSIMs) are popular within high-speed (HS) applications because of their high rotor structural integrity and their fairly well-established manufacturing process guaranteeing high quality series products. Designing a new HS electric machine requires a multidisciplinary team to accomplish the machine performance desired. In case of a HS machine design, the components and applied materials often reach their physical limits at the rated operating condition. Therefore, the design process is highly iterative and, thus, a systematic approach has a high potential to reduce the time of the design phase significantly. In this article, a systematic design process is proposed for a modular, multimegawatt (MMW) HSIM with three radial active magnetic bearings. The process includes a traditional multidisciplinary design flow with extra critical aspects of MMW HS machines: manufacturability, bearing system, housing, and operating unit. In addition, the manufactured machine is reported. The proposed systematic design process is described, including several multidisciplinary critical design aspects of HS machinery. [ABSTRACT FROM AUTHOR]

Application of energy storage (ES) in power distribution systems (PDS) of short sea shipping marine vessels is gaining ground. The main drivers are the increasing demand for higher energy efficiency and the decreasing costs of battery ES systems (BESS). The feasible chemistry and dimensioning of the BESS depend heavily on the vessel type, the PDS topology, and the load profile. Thus, no general rules for battery dimensioning that would fit all vessels can be presented, but the analysis must be performed by using an advanced modeling approach, which takes into account the abovementioned factors. This paper presents a modeling methodology for dimensioning marine vessel ES and hybrid PDS components. The methodology has been tested for two distinct vessels, a cruiseferry and an off-shore support vessel. [ABSTRACT FROM AUTHOR]

Driveline resonances are one of the major reasons for poor vehicle drivability, passenger discomfort, and premature wear of the mechanical parts of the driveline. Therefore, adequate models generated by system identification are essential in order to analyze resonances, and especially to design solutions to mitigate these adverse effects by means of control. In this paper, the resonating mechanical driveline of a hybrid city bus is identified by feeding different excitation signals, such as a pseudo-random binary signal, stepped sine, and chirp to the driveline, and by measuring the frequency response at a standstill and during on-road experiments. The identification experiments are conducted by operating the bus in the series electric hybrid mode, that is, in an operating mode that corresponds to a full electric mode powered by energy storages. Resonating two-mass system models are parametrized based on the obtained frequency responses and used to validate the identification experiments. [ABSTRACT FROM PUBLISHER]

High-speed (HS) electrical machines provide high system efficiency, compact design, and low material consumption. Active magnetic bearings (AMBs) bring additional benefits to the HS system, such as elimination of the friction losses, reduced wear and maintenance, and a built-in monitoring system. HS drivetrains are usually designed for specific applications and require a high level of integration. This paper describes a design method of the HS electrical machine supported by AMBs, considering their mutual influence on the system performance. The optimization procedure, which takes into account both the electrical machine and bearing designs, is developed. The optimization is based on a multiobjective genetic algorithm. The selected optimization parameters include the AMB and machine dimensions. The optimization objectives cover the electrical machine performance and the rotordynamics. The results of the proposed optimization algorithm are implemented in the constructed 350-kW, 15 000-r/min induction machine with a solid rotor supported by AMBs. The prototype tests verify the design and optimization results. [ABSTRACT FROM AUTHOR]

A proper real-time system identification method is of great importance in order to acquire an analytical model that sufficiently represents the characteristics of the monitored system. While the use of different time-domain online identification techniques has been widely recognized as a powerful approach to system diagnostics, the frequency-domain identification techniques have primarily been considered for offline commissioning purposes. This paper addresses issues in the online frequency-domain identification of a mechanical system with varying dynamics; particular attention is paid to detect the changes in the system dynamics. A closed-loop online identification method is presented that is based on a sliding discrete Fourier transform at a selected set of frequencies. The method is experimentally validated by a closed-loop controlled servomechanism with a limited stroke and time-varying parameters. [ABSTRACT FROM PUBLISHER]

The application of the gradient heat flux sensor as a failure and aging indicator of the power electronics was studied in this paper. Conducted experiments shown that the heat flux sensor attached to the insulated-gate bipolar transistor's (lGBT's) base plate can provide realtime heat flux monitoring. Condition monitoring (CM) model implemented in wind turbine based on online comparison of measured IGBT heat flux and expected power losses was proposed. The deviation of the measured heat flux from the expected power losses was detected during lGBT's package related failures. The maximum deviation of 30% was obtained from the module with broken bond wire. The lGBT's package related degradation mechanisms were modeled by the Finite Element Method (FEM) in order to validate experimental observations. The obtained results have shown that in order to accurately estimate the possible deviation of power losses of the degraded IGBT, the exact change in thermo-electric parameters of IGBT in different failure mechanisms, environmental conditions and operating temperatures should be taken into account. [ABSTRACT FROM AUTHOR]

Many control schemes rely on an analytical model of the servomechanism to be controlled, and hence, accurate knowledge about the position- and time-dependent parameter variability becomes crucial in many contexts, such as robust control methods. Although a properly designed robust controller can cope with a large parameter variation, real-time identification of the system parameter behavior could lead to several advantages by means of monitoring the varying dynamics, e.g., the predetermined uncertainty region around the nominal value. This paper addresses issues in online parameter estimation of a linear tooth belt drive with a limited stroke. Particular attention is paid to detecting the position-dependent changes in the system dynamics by using recursive least squares algorithm and exciting the system in different cart positions in order to identify the varying dynamics. The algorithm used is based on an indirect output-error identification scheme. The experimentally estimated parameters are compared with the corresponding two-mass model parameters. The results show an acceptable agreement and demonstrate the feasibility of the estimation method to estimate the parameters of a closed-loop controlled servomechanism with a limited stroke and time-varying parameters. [ABSTRACT FROM PUBLISHER]

A method is presented for tooltip tracking in active magnetic bearing (AMB) spindle applications. The proposed tool tracking approach uses control of the AMB air gap to achieve the desired tool position. A μ-synthesis-based controller is designed for the AMBs with the goal of robustly minimizing the difference between the tool reference and estimated tool position. In such a way, the model-based control approach concurrently addresses the tracking problem and the inability to directly measure real-time tool position in the presence of machining disturbances. To ensure the tractability of the control problem, a model of the desired tracking dynamics is included in the plant. The method is demonstrated on a high-speed AMB boring spindle. To confirm the tool tracking capability, characteristic part geometries are traced including stepped, tapered, and convex profiles. Tool tracking is demonstrated for the rotating AMB spindle in the range of 90 μm. Also, static and dynamic external loading is applied to the spindle tool location to confirm the disturbance rejection ability of the closed-loop system. [ABSTRACT FROM PUBLISHER]

Accurate and updated knowledge of the electric machine parameters provides benefits in many applications, such as model-based control methods. This paper presents an online parameter estimation method for double-star interior permanent-magnet (IPM) machines supplied with voltage-source inverters (VSI). The estimation method is based on a decoupled D–Q model of the machine and a recursive least-squares (RLS) algorithm. Initial machine parameters are estimated at a standstill. Then, in the rotating operating state, the inductances and the flux linkage produced by the PMs are updated. The estimation in the operating state is performed with a flux-linkage-based approach. The experimental results are compared with the corresponding values obtained from finite-element analyses. The results show an acceptable agreement and demonstrate the feasibility of the estimation scheme to estimate the parameters of double-star PM machines. The parameters are validated by comparing experimental and simulated open-loop responses and steady-state torques. [ABSTRACT FROM PUBLISHER]

Dual three-phase electric machines have many advantages compared with conventional three-phase machines. However, the properties of such machines present challenges for current control that make it difficult to produce sufficient performance for the electric drive. This paper introduces an improved vector control scheme for dual three-phase permanent magnet synchronous machines. The study includes detailed solutions for key parts of the control such as reference frame transformations, decoupling of the current control loops, and modulation. The performance of the suggested control scheme is evaluated using finite-element analyses and experimental results. The results show that the scheme can produce desired dynamics for the current control and guarantees balanced current sharing between the winding sets. In addition, the proposed solution is capable of reducing current harmonics produced by the internal structure of the machine. This problem is, however, only partly solved since complete elimination of harmonic components is not achieved. Nevertheless, the suggested control scheme overcomes many of the disadvantages found with other control solutions. Improved control performance allows the full benefits of dual three-phase drives to be utilized even in demanding applications. [ABSTRACT FROM PUBLISHER]