This paper describes the design method for Model Predictive Control (MPC) that is suitable for current control systems of Permanent Magnet Synchronous Motor (PMSM). A current control system based on MPC predicts future current behaviors for considerable input voltage and determines the optimum input voltage by evaluating these behaviors. Conventional MPC sets the cost function, making it effective for several control purposes. However, the suitability of the search space of conventional MPC has not been discussed and its achievable performance was limited. In this paper, we consider an appropriate search space for current control system of PMSM by referring to existing modulation methods and inverter operation. Then, we propose new MPC that satisfies that search space and show that the proposed MPC can usage from a linear region to a square-wave region by the appropriate search space.
The effective utilization of regenerative power generated by trains has attracted the attention of engineers due to its promising potential in energy conservation for electrified railways. Charge control by wayside battery batteries is an effective method of utilizing this regenerative power. Wayside batteries requires saving energy by utilizing the minimum storage capacity of energy storage devices. However, because current control policies are rule-based, based on human empirical knowledge, it is difficult to decide the rules appropriately considering the battery's state of charge. Therefore, in this paper, we introduce reinforcement learning with an actor-critic algorithm to acquire an effective control policy, which had been previously difficult to derive as rules using experts' knowledge. The proposed algorithm, which can autonomously learn the control policy, stabilizes the balance of power supply and demand. Through several computational simulations, we demonstrate that the proposed method exhibits a superior performance compared to existing ones.
In a power converter circuit, it is well known that the bus bar structure affects both surge voltage and switching loss. However, the bus bar structure may be one of the causes for the oscillation waveform to induce electromagnetic interference (EMI) issues. This study proposes a design procedure of an optimized bus bar structure. Since the parasitic parameters of the bus bar geometory, such as inductance, capacitance, and resistance, are complicated in the megahertz frequency range, the parasitic parameters that have frequency characteristics are analyzed by the finite element method. The surge voltage and oscillation voltage under a turn-off operation are evaluated by using the bus bar modeled as S-parameters. It demonstrated that the optimal bus bar structure can reduce the surge voltage and oscillation. In accordance with the method to design an optimal bus bar, bus bar prototypes are designed, and the experimental results rated at 400V, 30A are presented to verify the analysis and simulation.
Electric hand tools must be low cost and require minimal maintenance. To achieve these demands, a switched reluctance motor (SRM) is expected to be used as an electric hand tool motor as an alternative to a brushless DC Motor (BLDCM). The SRM is suitable for electric hand tools owing to its low manufacturing cost. However, the SRM has a disadvantage in that its torque density is lower than that of the BLDCM. Therefore, the SRM needs to add a higher current than the BLDCM to achieve the same output torque. Moreover, the winding temperature quickly increases owing to the large copper loss. To overcome this problem, this paper proposes a self-cooling SRM. The proposed SRM can realize the same output torque and the same volume as a BLDCM system including a fan. Additionally, the proposed SRM can slow the increase in winding temperature by increasing the motor volume and through the self-cooling effect. In this study, the performance of the prototype self-cooling SRM is verified through simulations and experiments.
The possibility of contact wire breakage due to AC arc discharge in electric railways has been qualitatively inferred based on the conditions of contact wire breakage in positive and negative DC arc discharge. However, railway operators need the precise threshold of the allowable continuous AC arc current with no possibility of contact wire breakage, because some breakage accidents occur at AC insulated overlap sections. In this study, the time until contact wire breakage against the arc current was experimentally measured. Then, heat conduction analysis was conducted to find the efficiency of heat transfer from AC arc discharge to the contact wire. Finally, an evaluation method for allowable continuous AC arc current with no possibility of contact wire breakage was proposed.
Recently, permanent magnet synchronous motor (PMSM) drive systems without the rotor position sensor are widely used as actuators in many applications. However, in the case of a pulsating load such as the compressors, the rotational speed of the motors is fluctuated and the drive system is vibrated due to the pulsating load torque. In this paper, we propose a new method to reduce the rotational speed pulsation. This method can seamlessly change the vibration suppression control and the high efficiency control. The simulation results indicate that the proposed method is very effective and practical.
This paper proposes a new mathematical model and simulator for permanent-magnet synchronous motors, which generate both magnet and reluctance torque ripples changing with the rotor position. The proposed model has the following features. (a) It. introduces a concept called “space-variability” of both rotor magnet and stator inductance, and successfully reproduce the magnet and reluctance torque ripples changing with the rotor position. (b) It presents new “proportional and differential torques” caused by the space-variable rotor flux and space-variable stator inductance. (c) It consists of three self-consistent basic equations, such as circuit, torque evolution, and energy transmission equations. (d) It has the generality in the sense that it is constructed in the general reference frame. The proposed simulator yields accurate reproductions of the current, flux, torque, etc. specified by the model. Moreover, it adopts the most compact structure using the vector signals in the general reference frame. The validity of the model is verified in a rigorous analytical manner and the usefulness of the simulator is demonstrated through simulations reproducing torque ripple that changes with the rotor position.
A number of machines have been fitted with electric motors and their inverters. To reduce the space of the motors and inverters, motors with two controllable rotors using a six-phase inverter have been proposed. However, the winding factor of three-phase and six-phase rotors in a conventional winding arrangement are 0.87 and 0.50, respectively. In order to improve the winding factor of the motor, we propose a novel winding arrangement and verify its effectiveness using finite element analysis.
Periodic measurement of the structure gauge is of extreme importance to ensure the safety of train operations. This measurement is labor intensive and time consuming because there is a considerable number of wayside facilities. Therefore, we have developed an inexpensive and efficient measuring equipment using laser range scanners. In addition, we have developed a management system that maps the measured three-dimensional point cloud data to the facilities data. This paper describes these problems, provides solutions for applying laser range scanners to structure gauging, and discusses the experimental results.
A bimetallic strip is a key component of thermal relays and molded-case circuit breakers, which are used to detect overcurrent faults in low voltage networks. Recently, a heat-insulated double-metallic (HIDM) strip was developed as an alternative for conventional bimetallic strips. It consists of two metallic strips bonded by a heat-insulated adhesive, and when an excessive current flows through the heater attached on one side of it, it deforms or bends due to the temperature difference. Because of its simplicity and low dependence on the ambient temperature, a high accuracy of current detection is expected. This paper shows that the performance of the HIDM strip can be improved by proper selection of the metal and design of its shape.
To increase the revenue of railway undertakings, yield management techniques can be adopted by setting up a quota for discounts on the ticket sales of reserved seats on express trains. We developed a method to calculate the optimum sales quota by estimating the demand for discount tickets and the behavior of passengers seeking the next-best options when they are not able to buy the tickets that were their first choice. We conducted a trial sale by applying the calculated sales quota to the actual seat reservation system and confirmed that the proposed method can increase revenue and facilitate decision-making for setting up sales quotas.