Two-leg three-phase inverter control for STATCOM and SSSC applications

Flexible ac transmission systems (FACTS) devices are attracting an increasing interest both in power system academic research and in electric utilities for their capabilities to improve steady-state performance as well as system stability. Several converter topologies for FACTS applications have been proposed in the recent literature, even if those based upon voltage source inverters (VSI) seem to be more attractive due to their intrinsic capability to rapidly respond to network changes such as perturbations subsequent to a fault and their property of being immune to resonance problem. In this paper, a new topology for inverter-based FACTS is proposed. This configuration, employing a two-leg three-phase inverter is employed for both series and parallel-connected reactive power compensators. The converter utilizes a modular topology for allowing a satisfaction of electronic components rating. A control strategy based on variable structure control technique with sliding mode is employed to track appropriate reference quantities. Design and control, as well as good tracking performances, are also verified through numerical simulations

Online thermal parameter identification for permanent magnet synchronous machines

Temperature monitoring of permanent magnet synchronous machines (PMSMs) is of great importance because high temperatures can significantly shorten the lifetimes of motor components. Accurate temperature predictions can be achieved using reduced-order lumped parameter thermal networks (LPTNs) with accurate thermal parameters. In this study, an online estimation method based on the recursive Kalman filter algorithm is introduced for online identification of the thermal resistances in a three-node LPTN representing motor stator iron, stator winding and permanent magnet. The identification procedure requires a rotor temperature measurement, which is provided by an accurate pulse-width modulation-based estimation method. The proposed methodology is experimentally validated and applied to real-time fault detection of the motor cooling system

Modelling framework for parallel SiC power MOSFETs chips in modules developed by planar technology

This paper presents a modelling framework to simulate transients and steady state performance for SiC power MOSFETs modules. The electro-thermal modelling is implemented using Simscape/MATLAB program based on the single chip characteristics provided in the datasheet. The method can easily incorporate multiple chips and module parasitic components providing a tool for module characterization and to support module design optimization. The simulated model is then experimentally validated at different voltage buses and junction temperatures for a novel SiC MOSFET Module design consists of two parallel chips per switch developed using wire-bond free planar technology

A general modelling technique for a triple redundant 3x3-phase PMA SynRM

A general modelling technique is proposed for a triple redundant 3x3-phase permanent magnet assisted synchronous reluctance machine (PMA SynRM). The magneto-motive force (MMF) of the machine is divided into three parts each associated with one 3-phase set. The MMF of each 3-phase set can be described by four variables: d- and q-axis components of the currents, the rotor angle and an MMF offset component which captures the mutual coupling between three 3-phase sets. Therefore the complete machine behavior in all operating conditions can be captured by means of 4-dimensional (4D) tables, which store the flux linkage and torque information. The 4D tables are produced by finite element (FE) analysis for one 3-phase set. As a result, the machine behavior can be predicted by interpolating the 4D tables. The model is capable of representing healthy and fault operations, including unequal current operation in three 3- phase sets, and offers great flexibility for performance assessment, post fault control and fault detection. Its effectiveness is verified by extensive FE simulation and experimental tests in different operation modes

Investigation into Fault Tolerant Capability of a Triple Redundant PMA SynRM Drive

Fault tolerant machine drives are being favored in safety critical applications, thus they are being actively investigated. However, most of the solutions address the winding or switch open circuit only, which is insufficient since intra-phase and inter-phase turn short circuits are more likely in the machine drives as a result of insulation degradation, and the consequences are usually catastrophic. Magnets and capacitor may also fail and cause damage during operation. All these faults should be properly addressed in fault tolerant machine drives for safety critical applications. Hence, a triple redundant, 9 phase (3x3phase) permanent magnet assisted synchronous reluctance machine (PMA SynRM) drive is presented by investigating the fault tolerances against various faults. The different fault behaviors are evaluated and the corresponding fault tolerant capabilities are analyzed. The machine fault tolerance is examined on a 35kW prototype drive. Both the analysis and experimental tests demonstrate that the machine drive exhibits excellent fault tolerant capability under most common types of faults, including the intra-phase and inter-phase short circuit, uncontrolled rectification, demagnetization and DC capacitor fault

Thermal modeling of hollow conductors for direct cooling of electrical machines

A direct cooling design using hollow conductors with the coolant flowing inside can significantly improve the heat dissipation in an electrical machine. To predict the thermal performances of an electrical machine with such cooling configuration, this paper proposes a computationally efficient thermal model of hollow conductors with direct cooling features. The hollow conductor is modeled using four equivalent solid cuboidal elements with a three-dimensional thermal network and internal heat generation. The heat transfer coefficient between the coolant and conductors is determined by an empirical model considering fluid dynamics behaviors. Axial discretization is performed to take into account the nonuniform temperature distribution along the axial direction. Experimental validation is performed with a U-shaped hollow conductor test rig. Compared to computational fluid dynamics analysis, the proposed thermal model is much more computationally efficient, and thus can be incorporated into design optimization process and electrothermal simulations of the electrical machine over a driving cycle

Active thermal management for Interior Permanent Magnet Synchronous Machine (IPMSM) drives based on model predictive control

This paper proposes an active thermal management scheme for Interior Permanent Magnet Synchronous Machine (IPMSM) drives based on the model predictive control concept. The proposed control scheme can adaptively set torque limit based on the thermal state of the machine to limit the machine winding and end-winding temperatures. The proposed control scheme is assessed by experiments on a laboratory machine drive system and simulated for traction drives over Worldwide Harmonized Light-duty Test Cycle (WLTC). Compared with conventional traction control scheme, the proposed scheme can effectively reduce peak temperature and hence thermal stress of the machine for improving its lifetime

Stator turn fault detection by 2nd harmonic in instantaneous power for a triple redundant fault-tolerant PM drive

Fast and reliable detection of stator faults is of key importance for fail-safe and fault tolerant machine drives in order to immediately trigger appropriate fault mitigation actions. The paper presents a detailed analytical and experimental analysis of the behavior of a closed loop controlled permanent magnet machine drive under inter-turn fault conditions. It is shown that significant 2nd harmonic components in the dq voltages, currents, instantaneous active power (IAP) and reactive power (IRP) are generated during turn fault conditions. The analyses further show that the increase of the 2nd harmonic in IAP and IRP during fault conditions is comparatively higher than that of voltage and current, making them ideal candidates as turn fault indicators. A turn fault detection technique based on 2nd harmonic in IAP and IRP is implemented and demonstrated for a triple redundant, fault tolerant permanent magnet assisted synchronous reluctance machine (PMA SynRM) drive. The effectiveness of the proposed detection technique over the whole operation region is assessed, demonstrating fast and reliable detection over most of the operating region under both motoring and generating mode

Experimental assessments of a triple redundant 9-phase fault tolerant PMA SynRM drive

Fault tolerant machine drives are key enabling technologies in safety critical applications. The machine drives are expected to exhibit high performance in healthy conditions and accommodate as many faults as possible, namely open circuit or short circuit in the machine and inverter or even an inter-turn short circuit. This paper aims to assess a triple redundant 9-phase (3x3-phase) permanent magnet assisted synchronous reluctance machine (PMA SynRM) drive by comprehensive experimental tests under both healthy and fault conditions on a 35kW machine drive prototype. The healthy performance, fault behavior, fault detection and fault mitigation strategy are presented and assessed by extensive tests which demonstrate that the machine drive exhibits high performance and excellent fault tolerance with simple and cost-effective implementation. Therefore, the proposed machine drive has proven to be a practical candidate for safety critical applications

Real-time Measurement of Temperature Sensitive Electrical Parameters in SiC Power MOSFETs

This paper examines a number of techniques for junction temperature estimation of SiC MOSFETs devices based on the measurement of Temperature Sensitive Electrical Parameters (TSEPs) for use in online condition monitoring. Linearity, sensitivity to temperature and circuit design for practical implementation are discussed in detail. A demonstrator based on the measurement of the quasi-threshold voltage, the turn-on transient characteristic (di/dt), the on-state voltage and the gate current peak is designed and validated. It is shown that the threshold voltage, the estimation of the gate current peak and the on-state voltage have potentially good sensitivity to temperature variation and linearity over a wide operating range. Very low sensitivity to temperature is shown for (di/dt). The proposed method can provide a valuable tool for continuous health monitoring in emerging applications of SiC devices to high reliability applications