This paper presents and compares control strategies for three-phase open-end winding drives operating in the flux-weakening region. A six-leg inverter with a single dc link is associated with the ...machine in order to use a single energy source. With this topology, the zero-sequence circuit has to be considered since the zero-sequence current can circulate in the windings. Therefore, conventional overmodulation strategies are not appropriate when the machine enters in the flux-weakening region. A few solutions dealing with the zero-sequence circuit have been proposed in the literature. They use a modified space vector modulation or a conventional modulation with additional voltage limitations. This paper describes the aforementioned strategies, and then, a new strategy is proposed. This new strategy takes into account the magnitudes and phase angles of the voltage harmonic components. This yields better voltage utilization in the dq frame. Furthermore, inverter saturation is avoided in the zero-sequence frame, and therefore, zero-sequence current control is maintained. Three methods are implemented on a test bed composed of a three-phase permanent-magnet synchronous machine, a six-leg inverter, and a hybrid digital signal processor /field-programmable gate array controller. Experimental results are presented and compared for all strategies. A performance analysis is conducted as regards the region of operation and the machine parameters.
Multiphase machines are well known for their fault-tolerant capability. Star-connected multiphase machines have fault tolerance in an open circuit. For an inverter switch short-circuit fault, it is ...possible to keep a smooth torque of a permanent magnet synchronous machine if the currents of the faulty phases are determined and their values are acceptable. This paper investigates fault-tolerant operations of an open-end five-phase drive, i.e., a multiphase machine fed with a dual-inverter supply. Inverter switch short-circuit fault is considered and handled with a simple solution. Original theoretical developments are presented. Simulation and experimental results validate the proposed strategy.
A general method for fault detection and isolation (FDI) is proposed and applied to inverter faults in drives of electric vehicles (EVs). This method is based on a change detection algorithm, which ...allows multiple fault indices (FIs) to be combined to retrieve the most likely state of the drive. The drive topology under study is a six-leg inverter associated with a three-phase open-end winding machine. Due to the inherent fault-tolerant topology, the conventional FIs are no longer effective. Therefore, an analysis of simulations under faulty conditions leads to the derivation of suitable FIs. These are based on the envelope of the phase currents, as well as their instantaneous frequency. Specific operating conditions related to the EV environment are taken into account, such as the flux-weakening region and energy recovery. In these modes of operation, FDI can be affected by uncontrolled currents circulating through the free-wheeling diodes. Finally, the performances of the FDI scheme are evaluated under steady-state and nonstationary conditions through simulations and experimental results.
This study deals with an on-line method for turn-to-turn short-circuit fault detection in low-voltage permanent-magnet synchronous machine drives. Owing to the closed-loop control, the fault effects ...are reflected in the voltage. Therefore an appropriate diagnostic index is proposed, which is derived from the positive- and negative-sequences of the voltage references. These sequences are obtained in the time domain via adaptive filters, which require only a few calculations. To increase the sensitivity to the fault, the algorithm is only applied to a part of the voltage references, that is, the output of the proportional–integral controllers. Furthermore, the cumulative-sum algorithm is introduced to cope with changes of small magnitudes. This algorithm allows a change of a fault index to be detected and can be used as a decision system. The resulting fault detection scheme is computationally cheap and can be embedded in the control unit. Simulations and experimental results validate the proposed method in steady state and the performances under non-stationary operating conditions are also investigated.
This paper analyzes two fault-tolerant dual-multiphase motor drives, a series-connected topology, and a standard H-bridge topology. Previous studies have shown that the series connected topology is ...appropriate to an aerospace application and has lower peak current in degraded mode in comparison with the H-bridge topology, which may consequently diminish the system's weight and cost. This paper extends the study to compare different control strategies of these structures under two fault conditions: short-circuit of an inverter's switch and an open-phase of the machine. The control strategies analyzed in this paper do not impact the fundamental current or the torque generation, but the amplitudes of some harmonics in degraded mode are expected to be narrowed down in order to reduce the inverter's size. Some analyses of maximum voltage and peak current in degraded mode have been used for inverter dimensioning. Experimental results are shown and compared to the simulated ones to confirm the validity of this study.
Multi-phase machines are well-known for their fault tolerant capability. Star-connected multiphase machines have fault tolerance in open-circuit. For inverter switch short-circuitfault, it is ...possible to keep a smooth torque of Permanent Magnet Synchronous Machine (PMSM) if the currents of faulty phases are determined and their values are acceptable. This paper investigates fault-tolerant operations of an open-end fivephasedrive, i.e. a multi-phase machine fed with a dual-inverter supply. Inverter switch short-circuit fault is considered and handled with a simple solution. Original theoretical developments are presented. Simulation and experimental results validate theproposed strategy.
This paper presents an extension of previous methods in order to find electrical series-connections between multiphase machines allowing the independent control of each one of them. These new ...electrical series-connections explore the symmetrical disposition of the phases of even-multiphase machines, allowing the inversed connection of some of the phases, different from the direct connections as it was previously done. Therefore, electrical series-connections of two symmetrical 6-phase or of four symmetrical 10-phase machines are now possible. Besides that, this new solution ensures a natural independent control of permanent magnet synchronous machines even if the back-electromotive forces generated by the rotor are not sinusoidal, without need of special machine conception or supplementary control strategy. This control independency ismathematically proved using the decomposition of multiphase machines in fictitious diphase and homopolar machines.Experimental results are presented to show the functioning and the advantages of this new coupling for two symmetrical 6-phasepermanent magnet synchronous machines.
This paper presents an extension of previous methods in order to find electrical series connections between multiphase machines, allowing the independent control of each one of them. These new ...electrical series connections explore the symmetrical disposition of the phases of even-multiphase machines, allowing the inversed connection of some of the phases, different from the direct connections as it was previously done. Therefore, electrical series connections of two symmetrical six-phase or of four symmetrical ten-phase machines are now possible. Besides that, this new solution ensures a natural independent control of permanent-magnet synchronous machines even if the back electromotive forces (back EMFs) generated by the rotor are not sinusoidal, without need of special machine conception or supplementary control strategy. This control independency is mathematically proved using the decomposition of multiphase machines in fictitious diphase and homopolar machines. Experimental results are presented to show the functioning and the advantages of this new coupling for two symmetrical six-phase permanent-magnet synchronous machines (PMSMs).
This study investigates a real-time fault diagnostic of a transportation system which needs two drives with fault-tolerance capabilities. Owing to the constraints on the mass of the system and on the ...cost of the voltage source inverter, a drive with two six-phase permanent magnet synchronous machines in series-connection supplied by two six-leg inverters is chosen. Despite the serial connection, independent control of the two machines and fault-tolerance to open-switch fault is ensured. Nevertheless, a fault detection identification (FDI) process is required for analysis and/or control reconfiguration. The proposed FDI is based on the combination of different criteria obtained from the two zero-sequence currents and from the normalised currents mapped into two frames defined by the concordia transformation. Results obtained from simulation and experimental tests show the effectiveness of the proposal.
PDF
