Degraded Mode Operation Research Articles

A review on proton exchange membrane multi-stack fuel cell systems: architecture, performance, and power management

To achieve carbon emission reduction and energy structure upgrading, the proton exchange membrane (PEM) multi-stack fuel cell system (MFCS) is an option to meet high-power demands in application scenarios. However, several barriers of the PEM MFCS have not been solved. This paper is aimed to summarize existing information and propose future R&D potentials. Firstly, detailed R&D activities and advances related to PEM MFCSs are reviewed including applications and design principle, architectures (fluidic, electrical, and thermal), power management strategy (PMS), water and thermal management, degraded mode operation, lifetime, efficiency, and hydrogen consumption. Among them, applications and design principle include application scenarios and influencing factors. Moreover, the architecture determination for MFCSs is the core issue, directly affecting the PMS, water and thermal management, degraded mode operation, lifetime, efficiency, and hydrogen consumption. It is noted that a MFCS is better than a single fuel cell system (SFCS) in fields of the lifetime, efficiency, and hydrogen consumption. Furthermore, the synergy between internal combustion engines (ICEs) and MFCSs is proposed to be applied for the MFCS R&D. Secondly, scientific challenges and prospects are presented, including effects of the load power-sharing on the lifetime and efficiency, comparisons of the performance, efficiency and lifetime, and control issues. Finally, the difference of several aspects is discussed, including the architecture, redundancy, lifetime, and PMS between a PEM MFCS and a PEM SFCS.

Use of the Dual Stator Induction Machine in Photovoltaic - Wind Hybrid Pumping

In this article, a combination of two renewable sources is used to power a pumping station. Indeed, a photovoltaic generator (GPV) and a wind turbine are installed so as to be complementary in the process of filling the water tower similar to an accumulator, before distributing the water by gravity. Prior knowledge of a few quantities, in particular the assessment of water requirements, total dynamic head (TDH) and flow rate is essential for sizing the various components of the pumping chain. The results obtained show that the combination of the energy of the sun with that of the wind ensures a continuity of service; the use of an engine (DSIM) and a double stator induction generator (DSIG) allows degraded mode operation in the event that one or more parts of the drive system are defective. The global system is dimensioned and simulated under Matlab/ Simulink Package.

An advanced control for a PM synchronous motor drive in power degraded mode

This paper deals with a control principle designed to allow remedial strategies for Permanent Magnet Synchronous Motor (PMSM) drives. The scope of the paper is focused on three-phase machines and it aims to present a simple and easy to tune control scheme for the system while it operates in degraded mode, namely when only two out of the three phases are operational. Compared to existing control strategy dedicated to degraded mode, this work proposes an innovative one using new reference frames. Based on two innovative transformations applied respectively to the currents and the voltages of the system, the proposed control scheme allows, in degraded mode, the decoupling control of the states of the system and leads to continuous controller references during system steady states. These properties lead to a very straightforward control scheme based on independent PI controllers and to high static and dynamic performances. The parameters setting of the controller is quite simple whatever the degree of magnetic coupling between the two remaining motor phases. A laboratory test bench has been built to establish a proof of concept of the suggested remedial strategy. It is based on a three-phase open-end-winding permanent magnet machine fed with a power inverter made of three full H-bridge. This experimental setup enables to validate the main operations of the ac motor drive under degraded mode operation: torque control, speed change. Switching between healthy mode and faulty mode is also performed successfully using this setup.

Degraded mode operation of multi‐stack fuel cell systems

Multi-stack fuel cell (MFC) systems provide higher performances and reliability than single-stack fuel cell systems through higher flexibility. The aim of this study is to investigate the degraded mode operation of MFC systems upon the loss of one of its stack. The different power allocation strategies impact the behaviour of the MFC system. Fuel consumption results obtained through simulation using a driving cycle acquired on a test vehicle are used to compare the chosen allocation strategies. The simulations have been conducted in a Matlab–Simulink environment. The results show that with a simple reconfiguration of the system the multi-stack system can still complete the driving cycle. The fuel consumption results during normal and degraded mode operation are compared and show acceptable efficiency loss during degraded mode operation.

An Error Model of a Complementary Filter for use in Bayesian Estimation - The CF-EKF Filter

It is well known that stand-alone inertial navigation systems (INS) have their errors diverging with time. Consequently an upper bound on the duration of INS systems precludes their use in low-cost micro unmanned aerial vehicles. The traditional approach for solving this matter is to resort to aiding devices, e.g., global navigation satellite system (GNSS) receivers, sighting devices, etc. Two philosophies have been extensively applied to perform data fusion: extended Kalman filtering (EKF) and complementary filtering (CF). Previous work in the literature showed that the computationally less expensive CF can be robustly applied to attitude estimation using low-cost sensors and achieve performance that is comparable to that of a full EKF. However, performance is degraded by vehicle manoeuvres and no measurement on estimate uncertainties is given. Furthermore, a large number of sensors makes it impracticable for optimal tuning of the CF. The present work lays the foundation for sensor filtering that employs the CF for attitude estimation by means of a magnetometer as an external aid, and an EKF for additional sensors integration. The main feature of this architecture is the possibility of deployment in a distributed multi-platform system and implementation of fault isolation by running the CF stage in a separate low-throughput reliable machine for stand-alone degraded mode operation. A case study is performed on synthetic data from inertial, magnetic and GNSS sensors.

A review of multi-stack and modular fuel cell systems: Interests, application areas and on-going research activities

Abstract Fuel cell technology is not widely used in the transportation industry because of its cost and technical and scientific barriers, which limit its efficiency, reliability and durability. Multi-stack fuel cell (MFC) systems could provide an improvement in performance over usual fuel cell systems. The aim of this paper is to present the current state of the art of multi-stack fuel cell systems. Different electrical and fluidic architectures have been designed for MFC systems. The effects of these architectures on the performances of the system are presented. Depending on the chosen architecture, a more reliable system is obtained through the enabling of degraded mode operation. The research focus is analyzed, and the remaining challenges are presented.

Reliability Considerations and Fault-Handling Strategies for Multi-MW Modular Drive Systems

Shunt-interleaved electrical drive systems consisting of several parallel medium-voltage back-to-back converters enable power ratings of tens of MVA, low current distortions, and a very smooth air-gap torque. To meet stringent reliability and availability goals despite the large parts count, the modularity of the drive system needs to be exploited and a suitable fault-handling strategy that allows the exclusion and isolation of faulted threads is required. This avoids the shutdown of the complete system and enables the drive system to continue operation. If full power capability is also required in degraded mode operation, redundancy on a thread level needs to be added. Experimental results confirm that thread exclusion allows the isolation of the majority of faults without affecting the mechanical load. As the drive system continues to run, faulted threads can be repaired and then added on-the-fly to the running system by thread inclusion. As a result, the downtime of such a modular drive system is expected to not exceed a few hours per year.

Two phase operation for a three phase PMSM using a control model based on a Concordia like transform associated to a classic Park transform

In aerospace applications, high reliability drives are required. For electrical drives based on three phase PMSM, a way to improve the reliability is to allow a degraded mode operation on two phases only, thanks to specifically developed power and control architectures. The aim of this paper is to present a control strategy for the two phase operation which is supported by a model based on a Concordia like transform associated to a classic Park transform. This approach maintains the advantages related to the torque control in the Park reference frame: the two active phases are still supplied with sinusoidal currents, whose amplitude is proportional to the torque. By adjusting the phase shifts between these currents and the corresponding electromotive forces (EMFs), the torque ripple can be minimized or even canceled according to the EMF shape.

Clustered RAID Arrays and Their Access Costs

RAID5 (resp. RAID6) are two popular RAID designs, which can tolerate one (resp. two) disk failures, but the load of surviving disks doubles (resp. triples) when failures occur. Clustered RAID5 (resp. RAID6) disk arrays utilize a parity group size G, which is smaller than the number of disks N, so that the redundancy level is 1/G (resp. 2/G). This enables the array to sustain a peak throughput closer to normal mode operation; e.g. the load increase for RAID5 in processing read requests is given by α = (G - 1)/(N - 1). Three methods to realize clustered RAID are balanced incomplete blocks designs and nearly random permutations, which are applicable to RAID5 and RAID6, and RM2 where each data block is protected by two parity disks. We derive cost functions for the processing requirements of clustered RAID in normal and degraded modes of operation. For given disk characteristics, the cost functions can be translated into disk service times, which can be used for the performance analysis of disk arrays. Numerical results are used to quantify the level of load increase in order to determine the value of G which maintains an acceptable level of performance in degraded mode operation.

The Honeywell/DND helicopter integrated navigation system (HINS)

The development of prototype of a high-performance, fault-tolerant navigation system for Canada's anti-submarine-warfare helicopter is discussed. HINS consists of three primary navigation subsystems (an F/sup 3/INS, a five channel P-code GPS (global positioning system), and a Doppler velocity sensor) and three secondary sensors (a strapdown magnetometer, a vertical gyro, and an air data system). The system is designed to blend the complementary strengths of component sensors, and to provide graceful degradation of performance in the event of failure or slow deterioration of these sensors. During normal operation, the Doppler and secondary sensors are calibrated to enhance performance during degraded mode operation. A multilevel failure-detection and -isolation scheme monitors sensor health and identifies faulty system components. HINS automatically reconfigures itself to optimally integrate remaining components. The system will operate in the event of an INS failure and also provides a worst-case limp-home capability using only the air data system and the magnetometer. The analyses in the original feasibility study and the architecture that is being implemented in the advanced development model are described. >