Yves Mollet

Current sensor fault detection and isolation combining model-based and signal-based algorithms in PMSG drives

This paper presents a new on-line open-phase and current-sensor fault detection and isolation method for permanent-magnet synchronous generator (PMSG) drives with neutral point voltage control. Simple signal processing implementations for sensor outage and open-phase faults detection are combined with a cumulative-sum (CUSUM) algorithm capable of detecting smaller sensor output errors (offset or gain variation). The algorithm uses output signals from eight current sensors (two on each phase and two on the neutral wire). Experimental tests have been done on a 2kW-PMSG at different speeds and braking torques where different sensor-fault combinations have been tested with and without open-phase fault. Finally a test has been done while the shaft speed and the torque were varying in order to test the ability of the algorithm to work in transient conditions. Results show that the algorithm allows 3-out-of-6 redundancy in case of sensor outage and 5-out-of-6 redundancy in case of sensor offset or gain change with globally limited computational cost. Combinations of two outages and one offset or gain error can be isolated. In case of open-phase fault the algorithm can continue to detect sensor faults if at least one sensor is working on each remaining phase and on the neutral. A short fault detection time is obtained in case of sensor outage with a transitional detection by the CUSUM algorithm followed by the final detection by the signal processing algorithm.

Rotor-current and position estimator for doubly-fed induction generators - application to sensor-fault detection

A combined encoder and rotor-current-sensor fault detection and isolation algorithm for doubly-fed induction machines is presented. A rotor-position and current estimator based on air-gap power vector computation is used for residual generation. A cumulative-sum function permits detecting and isolating the investigated faults. The algorithm is experimentally tested on a 3 kW generator in steady and transient regimes. Sensor outages as well as current-sensor gain drifts and offsets are investigated. Transients do not significantly affect the algorithm, which also allows for a very short detection time for the most critical faults.

Model-based design and testing for electric vehicle driveability analysis

In this paper a model-based design and testing method focusing on the electric vehicle driveability aspect is proposed. The design approach is divided into two steps. The first step is the Model-in-the-Loop co-simulation coupling a vector-controlled electric drive modelled in MATLAB/Simulink to a planar forward-facing electric vehicle LMS Imagine. Lab Amesim model. The second step represents a mechanical-level Hardware-in-the-Loop test for a physical electric drive that integrates the electric vehicle model in the real-time testing case. Two different sampling times of the vehicle control unit are considered and their influence on the vehicle responsiveness and on the longitudinal jerk acting on the driver is analysed through both offline simulation and real-time testing.

Detection and isolation of asymmetrical short-circuit faults in permanent-magnet synchronous machines

Phase-to-phase short-circuit faults in a permanent-magnet synchronous machines are quite dangerous because of the extremely high short-circuit transient current after fault. This paper presents a fault detection and identification diagnosis approach for asymmetrical faults in permanent-magnet synchronous machines, considering both inter-turn and phase-to-phase short-circuit faults, and employing both current- and voltage-based residual along with the cumulative-sum algorithm. The sum of positive- and negative-sequence current- and voltage-phase angles is used to identify the faulty phase(s); the two fault types are distinguished by defining different detection thresholds for the residuals. Simulations of phase-to-phase short-circuit with different short-circuit resistance have been carried to obtain the values of faulty phase indicators. Both the simulation results and the proposed diagnosis have been verified by practical experiments on a 2-kW test bench.

Experimental noise and vibration analysis of switched reluctance machines comparison of soft and hard chopping in transient conditions

This paper presents a comparison of soft and hard chopping on an 8/6 SRM in terms of noise, vibration and harshness. Transient-state measurements are used to plot speed-frequency signatures of current, vibration and acoustic noise of the SRM for different load torques. With this technique speed-related frequencies can be distinguished from resonance frequencies, and therefore, more information can be extracted from the plots. The results show that hard chopping increases the loudness of acoustic noise compared to soft chopping, with a frequency shift to higher values. This however leads to an attenuation of the vibration and noise amplitudes at the most critical resonance of the SRM, situated at a relatively low frequency.

Mechanical-State Estimator for Doubly-Fed Induction Generators - Application to Encoder-Fault Tolerance and Sensorless Control

In this paper a new model reference adaptive system observer for estimating the mechanical quantities of a doubly-fed induction generator, namely position, speed and electromagnetic torque and power, is presented. It is based on the computation the air gap power vector, considering saturation by using a variable magnetizing inductance. This algorithm can be used as a back-up in case of encoder fault thanks to an associated fault detection and isolation technique, combining a cumulative-sum function and a state-space adaptive model. Experimental tests on a 3 kW 4-pole doubly-fed induction generator show that a varying magnetizing inductance is recommended if the reactive power flow at stator terminals has to be varied in a large range. The encoder-fault detection time does not vary significantly with speed, torque or stator reactive power flow.

LCL Filters for a grid emulator application - Comparative study of active damping techniques

This paper focuses on the implementation of LCL filter active damping in the control of an inverter for a three-phase grid emulator application. The studies about LCL damping in the literature focus on the case of an inverter injecting current into the grid while a grid emulator application is rather about establishing correct voltage waveforms and emulating the grid for any kind of load connected to it, which brings a different perspective. After having analyzed the stability of the LCL filter taking into account possible load variations, three damping methods are compared and assessed with respect to those concerns.

Influence of 2D and 3D meshes in FE computation of eddy-current losses in surface PMSMs

This paper investigates the influence of finite-element (FE) mesh when computing eddy currents in magnets of a permanent-magnet synchronous machine excited with pulsating currents (such as pulse-width modulation). 3D computations with globally and locally varying mesh densities are performed and results are compared with a reference (fine-mesh) case. It turns out that a global increase of mesh density has the most important impact on the result accuracy. The accuracy of 2D FE computations is also discussed for different stack lengths. It is shown that the use of a correction factor based on analytical approach can significantly increase accuracy for relatively short stack lengths.

DC Voltage Control of a Wide-Speed-Range Permanent-Magnet Synchronous Generator System for More Electric Aircraft Applications

This paper proposes an interior-permanent-magnet synchronous generator suitable for wide-speed-range operation and its DC voltage control strategy, which makes this system a promising candidate for 270V DC power system in more electric aircraft applications. The machine is designed and manufactured to have a strong field-weakening capability. An active rectifier is utilized for DC-link voltage stabilization with field-oriented control. The active damping technique is considered in the PI controller, which can shorten the transient of the DC-link voltage when the load changes. Design consideration on strengthening the PM machines field-weakening ability is briefly presented, and a prototype has been built and tested. The proposed field-oriented control with the active damping has been implemented in simulation over a speed range of 150~1500rpm, changing from no-load to load condition. Experimental tests are also carried out in order to verify the effectiveness of the proposed system.

Finite-element and magnetic-equivalent-circuit modelling of brushed wound-field DC machines with cross-saturation

This paper deals with the two-dimensional (2D) finite-element (FE) and magnetic-equivalent-circuit (MEC) modelling of an existing 10 kW brushed wound-field DC machine, taking magnetic cross-saturation into account. The 2D FE model allows to thoroughly investigate the demagnetizing effect of the armature current on the pole flux and the cross-saturation effect on the field and armature-winding flux linkage. A minimum-topology MEC, allowing for these effects is proposed. Some of the reluctances are fitted stepwise using the FE model. It is shown that the simple MEC generates comparable results also at no-load and load conditions, but with highly reduced computational costs. All numerical results are validated experimentally.