1,720,983 research outputs found
Sensorless Control with Indirect Field Oriented Speed Estimation for Seven-Phase Induction Machines
No full textMultiphase machines offer more degrees of freedom than conventional three-phase machines. Thus, a multiphase drive can control multiple spatial harmonics independently of each other. With the torque generation in the 1 stvector space, this paper proposes to inject currents in the 3rd vector space for the speed estimation thus realizing a sensorless control scheme. At lower mechanical speeds, the back-EMF decreases and becomes more difficult to estimate as the signal-to-noise ratio decreases. Injecting a slip increases the stator frequency, which in turn allows a better estimation of the back electromotive force. An experiment showing a start from standstill conditions demonstrates the proposed control
Sensorless Control for Six-Phase Permanent Magnet Synchronous Machines Based on Back-Electromotive Force Estimation
No full textThis paper presents a sensorless control algorithm based on back-electromotive force estimation for a six-phase permanent magnet synchronous machine drive. The proposed solution employs a hybrid state observer that uses two different flux estimators. To find the rotor flux position, the first observer uses the fundamental harmonic of the magnetic field, while the second observer uses the fifth harmonic. The control scheme fully exploits the degrees of freedom of multiphase machines and reduces the dependence on electrical parameters that may vary during motor operation. The experimental results confirm the robustness of the proposed solution and its independence from machine parameters. The experimental tests also demonstrate the satisfactory dynamic response and stable behavior of the drive at low speeds
Voltage Balancing Analysis of DC-Link Capacitors in Six-phase Three-Level T-Type Inverters
No full textThe request for converters with high power density, efficiency, and reliability poses increasing design challenges. To meet this request, two technologies have established themselves in recent years: multi-phase and multilevel converters. Each of them allows the power level and reliability of the system to increase. One of the most traditional issues of multilevel converters is the voltage unbalance of the dc-link capacitors. This problem can be solved in a multi-phase multilevel converter through the numerous degrees of freedom typical of this technology. A technique capable of nullifying the voltage oscillations for six-phase three-level inverters is presented in this paper. The proposed solution can also reduce the number of commutations in the switching period while the voltage oscillations are suppressed. Finally, the developed solution is compared with the double three-phase counterpart with two isolated dc-bus neutral points to underline the advantages. Experimental tests have been carried out on a six-phase induction motor with two isolated three-phase star-connected stator windings to validate the proposed solution
High-Torque Density and Voltage Overmodulation for Five-Phase Induction Motor Drives
Full text linkThe torque density of a multiphase motor can be increased without exceeding the admissible current of the drive if the high-order spatial harmonics of the magnetic field in the air gap are appropriately synchronized with the fundamental one. Notably, due to the converter voltage limitation, this method is feasible only if the speed of the rotor is below its base speed. As the speed of the rotor increases, the voltage must correspondingly increase to sustain the field harmonics in the air gap. Above the base speed, the prevalent strategy in motor control focuses on regulating only the fundamental component of the magnetic field in the air gap. Nevertheless, this paper presents a new method that employs the injection of voltage harmonics to extend the linear modulation range of the fundamental voltage vector, thereby improving motor performance. In the field weakening region, an increase in the magnitude of the stator voltage vector improves the motor power and torque by over 40%. Experimental tests on a five-phase induction motor drive confirm the feasibility and the effectiveness of the developed control scheme. Overall, this approach shows great potential for improving motor performance and has applications in various sectors of motor control
Voltage Balancing of the DC-Link Capacitors in Three-Level T-Type Multiphase Inverters
Full text linkThis paper illustrates an algorithm to balance the voltages across the DC-link capacitors of a three-level multiphase inverter feeding a star-connected load with an odd number of phases. The proposed strategy keeps the DC-link capacitors balanced in any operating condition and minimizes the low-frequency voltage oscillations, even during open-phase faults and with non-sinusoidal output currents. Finally, the paper identifies the operating region where the voltage oscillations of the DC-link capacitors can be canceled. The developed algorithm can maintain constant voltages even if the capacitors are unbalanced, and its performance is compared to that of other carrier-based algorithms. Experimental tests are carried out on a five-phase induction motor in healthy and faulty conditions
Detection of Trailing-Edge Demagnetization for Six-Phase Permanent Magnet Motors
No full textThe trailing edge demagnetization in Surface-Mounted Permanent-Magnet Synchronous Motors (SMPMSMs) is commonly the result of an excessive torque overload. This fault irreversibly reduces the torque constant and motor efficiency, and it is often difficult to diagnose in three-phase machines for small demagnetization angles. Conversely, multiphase drives providing additional degrees of freedom make it possible to develop new potential diagnostic algorithms that are more accurate and robustThis paper proposes a diagnostic algorithm for the online detection of rotor demagnetization faults for six-phase machines with parallel magnetized rotor magnets. The proposed technique directly quantifies the demagnetization angle and actively corrects the angular position of the control system to ensure maximum motor performance in post-fault conditions. Experimental tests have been carried out on two identical six-phase PMSMs differing only in the size of the rotor magnets to emulate the effect of a trailing edge demagnetization. The experimental results confirm the effectiveness and robustness of the proposed solution
Fault-Tolerant Control Strategies of Five-Phase Induction Motor Drives under Open-Switch Fault
Full text linkWhen an open switch fault occurs, a power switch in a converter leg is always open while the corresponding freewheeling diode can still conduct. This type of fault is usually caused by some problems in the driver circuits or the PWM communication system.An open-switch fault is usually treated as an open-phase fault, but new control strategies with improved performance can be developed specifically for this type of fault.In this paper, four different control strategies against an open switch fault are presented and compared in terms of stator Joule losses and torque ripple. A motor control scheme for multiphase induction motor drives is developed and assessed.The feasibility of the proposed solution is verified by means of experimental tests on a prototype of five-phase induction motor
Five-to-Three Phase Doubly-Fed Induction Machine for Wireless Energy Transfer in Rotary Assembly Stations
No full textRotary assembly stations are commonly used in automated manufacturing processes. One of the problems that designers have to address is how to supply the electric actuators, sensors and controllers located on the rotating disk of the machine. These requirements are usually met through a gearmotor and sliding electrical contacts. However, slip-rings suffer from aging and thus a scheduled maintenance program is required. This paper avoids the use of slip-rings by means of an integrated electric drive consisting of a gearless multiphase induction machine with different numbers of stator and rotor phases fed by two inverters, one placed on the stator frame and one placed on the rotating one. The theoretical analysis derives a control algorithm that can decouple the torque control from the power transfer control.The feasibility of the proposed drive and the accuracy of the machine model is supported by analytical and finite element simulations
Local Demagnetization Detection in Six-Phase Permanent Magnet Synchronous Machines
Full text linkThe partial demagnetization process in surface-mounted permanent-magnet synchronous motors (SMPMSMs) negatively affects the performance of an electric drive, reducing the rated torque and the efficiency of the machine. This article presents a comprehensive analysis of the rotor demagnetization caused by an overcurrent event for a six-phase SMPMSM. Multiphase drives may become a key solution for safety-critical applications because they allow one to increase the intrinsic reliability of electric systems and monitor the health state of electric motors and power converters. This article proposes a diagnostic algorithm for the online detection of rotor demagnetization faults that also considers the magnetization direction of the magnets. The effects of the parallel or radial magnetization of the rotor magnets are analyzed for multiphase machines. The technique quantifies the demagnetization degree to estimate the fault severity and corrects the angular position of the encoder to ensure maximum motor performance under postfault conditions. Experimental tests have been carried out on two identical six-phase PMSMs differing only in the size of the rotor magnets to emulate the effect of trailing-edge demagnetization. The experimental results confirm the effectiveness and robustness of the proposed solution
Open-Phase Fault-Tolerant Pole Transition Control of an Asynchronous Variable-Pole Machine Using Harmonic Plane Decomposition
Full text linkAutomotive applications are revisiting the use of induction machines as magnet-free propulsive solutions due to their intrinsic robustness and reliability. Special multiphase configurations are under investigation to reduce the losses further and fulfill the stringent energy-efficiency and compactness requirements of the automotive industry. One of these configurations is known as variable-pole machines, which allows the number of magnetic pole pairs to change on the fly. These machines can stretch the torque-speed operating region, exploit the maximum torque capability, and exhibit competitive efficiency. Although fault tolerance has been widely explored for multiphase machines, the same cannot be said for variable-pole machines because, until recently, complete models to describe their dynamics under any condition, including magnetic pole changing and fault occurrences, were unavailable. This paper presents a post-fault control strategy for variable-pole machines with an open-phase fault, which can operate during pole changing and addresses the issue of fault-tolerant operation. The effectiveness of the control system is verified by experimental tests carried out with an eighteen-phase variable-pole induction machine prototype
- …
