Iet Electric Power Applications最新文献

Recently, Modular Multilevel Converters (MMC) are considered to be extensively used in medium-voltage AC drives A two-stage deadbeat-based strategy is developed by the authors to make the implementation of Predictive Torque Control (PTC) technique for an induction motor that is fed by a three-phase MMC possible . Despite various benefits of PTC strategy, it has not been widely employed for multilevel topologies due to the huge number of switching states of these converters, and the complex internal dynamics of topologies such as MMC. The proposed control scheme results in significant reduction of the computational burden, using an initial reference voltage that is determined at the first stage of the strategy by the deadbeat technique. Next, the predictive evaluation process is conducted at the second stage to simultaneously control the stator flux, electromagnetic torque and circulating current. The number of admissible vectors that should be evaluated in the cost function is effectively limited by only considering some adjacent vectors of the reference voltage in the first stage. Moreover, the circulating current control capability, which is necessary for effective operation of MMC, is also considered in the developed scheme. Finally, the satisfactory performance of the proposed strategy is validated through various experimental tests.

The segmental translator linear switched reluctance motor (STLSRM) is a special type of linear switched reluctance motor (LSRM) that has more output power than its conventional type. Therefore, it can be a good choice for certain applications. Heat is one of the factors limiting the output in machines. Therefore, predicting the thermal distribution of machine is as important as the magnetic design. A comprehensive thermal model is presented based on the lumped parameter approach for STLSRM, which predicts temperature distribution in different parts of this motor, including slot winding, end-winding, stator pole, stator yoke, and the moving part. Considering that the proposed thermal model depends on dimensions and materials used in machine, it can be used for other designs of the STLSRM. The presented thermal model is applied to a typical STLSRM and temperature is determined in its different parts. The simulation results are then compared with the results of 3-D thermal modelling based on the finite element method (FEM) for validation.

Brushless power generation sets are a technology of choice for on-board power generation in aerospace and marine applications, emergency and backup power systems, etc. Efficient modelling of these systems is necessary for various purposes such as design, analysis, control and specially condition monitoring. An accurate and efficient model of a diesel-engine generator-rectifier system consisting of a three stage brushless synchronous generator is presented. The constant parameter voltage-behind-reactance model of the pilot exciter (PE), main exciter (ME) and main generator are derived and integrated to form a unified model suitable for efficient simulation of a diesel-engine brushless generation system. Simulation studies are carried out in MATLAB using PLECS toolbox and the results are compared to experimental results to verify the performance of the proposed integrated model.

To compensate for the influence of temperature on the efficiency of an ultrasonic motor (USM), this paper proposed a maximum efficiency point tracking control method for temperature drift by analysing the relationships between the maximum efficiency point and the voltage and frequency of the driving circuit. The method first calculates the frequency update step of the driving circuit by the polynomial surface fitting method, considers the influence of temperature rise on the voltage-efficiency-frequency characteristics, and then adjusts the frequency in real time to compensate for temperature effects. Simulation and experimental results show that our method can improve the USM performance at the maximum efficiency point under changing temperature. Maximum efficiency point tracking algorithm with temperature compensation algorithm achieves maximum efficiency in experiment.

In recent years, the extensive participation of turbine generator in deep peak regulation has caused significant damage to the rotor windings, which is rooted in the frequent and significant changes in the electrical load of the rotor, accompanied by thermal expansion and contraction, causing harm to the rotor insulation and stress fatigue of the metal conductor. Hydrogen, as the cooling medium for the rotor windings of turbine generators, has a direct impact on the windings temperature through its parameters. Starting from suppressing the harm of deep peak regulation on the rotor windings, the inhibitory effect of hydrogen parameter changes on the temperature of the gap-pickup diagonal-flow rotor is studied. A calculation model for the rotor temperature field of the turbo-generator with gap-pickup diagonal-flow ventilation is established. The finite volume method is used to iteratively calculate the control equations in the fluid-thermal-solid coupling heat transfer problem, and the temperature field distribution of various components of the rotor under different excitation loads is obtained. On this basis, the effects of individual adjustment of hydrogen temperature and pressure, as well as the combined adjustment, on the temperature of the rotor windings are studied. Finally, a variable hydrogen parameter adjustment strategy is proposed for the operation of turbo-generators under deep peak regulation conditions. To a certain extent, the winding temperature fluctuation can be suppressed, which provides a potential solution for the thermal stable operation of the rotor.

When dealing with safety-critical applications that involve multiphase permanent magnet synchronous motors (PMSMs), the current source inverter (CSI) is a superior choice compared with the voltage source inverter. The conventional technique of pulse width modulation (PWM) presents a challenge for CSI, particularly during faults. The fault-tolerant control of multiphase PMSMs fed by CSIs has not been well investigated, particularly in situations involving double-phase open-circuit faults. Furthermore, fault-tolerant control becomes more complex when the multiphase PMSM includes harmonic back electromotive forces (EMFs). To deal with these issues, an ampere-second (AS) vector PWM technique is developed for a five-phase PMSM powered by CSI11. The modulation ratio of the proposed PWM is identical to that of space vector PWM. The proposed method, however, is easier to implement. A fault-tolerant control method using AS-vector is proposed for single-phase, adjacent double-phase, and non-adjacent double-phase open-circuit faults. Additionally, a method is developed to suppress the torque ripple that results from harmonic back-EMFs during fault conditions. Compared without the torque ripple suppression method, during the speed rising, the proposed method can reduce torque ripple to 16.7%, 54.5%, and 37.5%, respectively. The experiments have confirmed the effectiveness of the proposed PWM technique and fault-tolerant control method.

The adverse effect on speed ripple and vibration makes it necessary to evaluate the cogging torque. Due to the tolerance of stator and rotor stacks as well as nonuniform magnetization of permanent magnet, the amplitude of cogging torque is unequal in different rotor position. As a result, the verification of theoretical analysis becomes difficult. Therefore, the cogging torque average is used to weigh it. In view of the large least common multiple of multi slot/pole Permanent magnet motor, which means, there are multiple cogging torque cycles per rotor revolution, a cogging torque measurement method is proposed. Through simple devices such as arm, weight, digital gauge, resolver, and so on, the amplitude and period of cogging torque can be accurately measured without site restrictions. The correctness of the method is verified by simulation and experiment, and that can be used as a supplement to cogging torque evaluation for multi slot/pole PMM.

Direct Instantaneous Torque Control (DITC) with an adaptive turn-on angle technique is presented in this paper to improve the torque ripple of the Switched Reluctance Motor (SRM) for Electric Vehicle applications. Torque ripple suppression is achieved by employing two operating modes during the commutation interval. First, both the outgoing and incoming phase states are modified to track the required torque during the incoming phase's minimum inductance area. As soon as the incoming phase leaves its minimum inductance zone, the outgoing phase is demagnetised, and only the incoming phase state is modified for torque tracking. In addition, a closed-loop regulator is used to dynamically control the turn-on angle that drives the incoming current to reach its first peak at the instant of switching between the two operation modes when the rotor and stator poles initiate overlap, thus increasing the motor's efficiency. Simulation results showed that the proposed control method has superior advantages over the traditional DITC and Average Torque Controller. Furthermore, the simulation results were verified experimentally using a four-phase 4kW, 8/6 SRM prototype.