Recently development of power electronics technology has made it possible to realize a ultra high speed drive and a ultra high speed drive has been expected in various applications. This research aims at sensorless control drive of induction machine in the ultra high speed region by utilizing rotor slot harmonics, which occur due to structure of induction machine. In this paper, we focus on the slot harmonics which appear to a neutral point voltage, and we propose a detection method of slot harmonics voltage and a speed estimation method utilizing FFT with limitation of detection band. Moreover, the effectiveness of the proposed method and possibility of speed sensorless control with proposed method is illustrated through speed estimation results of off-line and on-line.
In railways, fixed timetables are provided day by day at present, meaning that those timetables do not fit passengers' demand of each occasion. In this paper, we propose an idea to dynamically change train timetables reflecting passengers' demands so that passengers can be provided with better transportation services. To realize this idea, we introduce a train timetabling algorithm which organizes train timetables directly from passengers' demands. Unlike conventional works, the algorithm takes all passengers' disutilities into account by estimating each passenger's behavior towards a train timetable, and produces a timetable in which passengers' disutilities are minimized and efficiency of resource utilization is maximized. Hence, this algorithm takes passengers' demands as its input and outputs a near optimal timetable from the viewpoints of the criteria described above. We have conducted several experiments using the data which were made from actual railway lines and shown that the algorithm is capable of producing timetables which properly fit the passengers' demands.
This paper addresses quantization of control systems. The state of the system is quantized via a quantizer. In addition, constraints on input and/or state are considered explicitly. For a linear system with no constraint, some quantized feedback control methods have been proposed. In this paper, a control methodology for the constrained system is proposed. Specifically, an idea of a positively invariant set is introduced so that the performance is improved while the constraints are satisfied. The effectiveness of the proposed method is verified through both simulation and experiment.
This paper proposes a new voltage controller of self excited induction generator. The nature of self excitation in an induction generator makes its output voltage very dependent on the amount of reactive power at generator terminals. The proposed scheme utilizes a continuously controlled shunt capacitor, which is called SVC magnetic energy recovery switch (SVC MERS), in order to realize voltage regulation of the system. The proposed system consists of a bi-directional current switch, dc capacitor and inductor as a filter. Two types of experiment were conducted to perform voltage control in load varying conditions at constant and variable speed. Experimental results performed that this system has the following advantages: i) simple control, where only two voltage sensors are required and voltage feedback control with PI controller gives a good response, ii) low switching frequency with zero current turn on and zero voltage turn off and resulting low switching losses. The proposed system is proved to have good performance when being applied as a voltage regulation to induction generator.
A new vector control system for permanent magnet synchronous motor drives has been developed. To stabilize the current control loop in the high rotating speed region, a novel configuration of current controller is introduced. The unique characteristic of the proposed current controller is that the current regulator is connected to the conventional motor model in a series. By analyzing the transfer characteristics of the control, it became clear that the influence of the coupling component between d-q axes can be deleted theoretically if the control parameters are set properly. Stability and torque response of the proposed vector control system were improved. Effectiveness of the proposed controller was demonstrated by a time domain simulation and, some experiments. In addition, the robustness of the controlling system was investigated in some experiments.
This paper describes a gate drive circuit which is capable to drive an ultra high-speed switching device and to suppress a high-frequency noise caused by its high-dV/dt rate of 104-V/μs order. SiC (Silicone Carbide) based power semiconductor devices are very promising as next generation ultra high-speed switching devices. However, one of their application problems is how to drive them with less high-frequency noise without sacrificing their ultra high-speed operation capability. The paper proposes a new gate drive circuit specialized for such devices, which charges and discharges the input capacitance of the device by using an impulse voltage generated by inductors. This ultra high-speed switching operation causes the high-frequency common-mode noise current in the gate drive circuit, which penetrates an isolated power-supply transformer due to the parasitic capacitance between the primary and the secondary windings. In order to overcome this secondary problem, a toroidal multi-core transformer is also proposed in the paper to reduce the parasitic capacitance drastically. By applying the former technique, the turn-on time and the turn-off time of the power device were shortened by 50% and by 20%, compared with a conventional push-pull gate drive circuit, respectively. In addition, the latter technique allows suppressing the peak common-mode noise current down to 25%, compared with a case of using a conventional standard utility power-supply transformer.
This paper presents a simple voltage control system of AC machines using PWM voltage source inverter with output LC filters. By assuming a motor as a current source, the voltage is controlled by a simple proportional differential (PD) control. The vector control and PD control can be separately controlled in this system. A method for disturbance rejection is also described. The effectiveness of the proposed method is verified by simulations and experiments.
Robots working in unknown environment or human environment have been researched for years in the field of motion control. For the next generation robot, human and robot interaction technologies are needed. Especially, abstractions of human motion and motion display technologies are important. This paper proposes a method for haptic motion abstraction based on action force directionality. Action force is measured by using the master-slave robot hand system which is bilateral controlled. Human motion is abstracted as action modes and action ratios, which are calculated from action force directionality. Action modes are expressing action force directionality, and action ratios are expressing amplitude of each action modes. Action modes are valid for motion preservation, identification of human and motion display system. Thus, as one of the application of action modes, a method for motion display is also proposed. Motion display control system is designed based on action modes and action ratios. This control system presents desired action force directionality as velocity response depending on human action force. The validity of the proposed method is shown by the experimental results.
Renewable energy sources such as wind turbine generators and photovoltaics are intermittent in nature, thus resulting in fluctuating electric power. Leveling of their electric power is indispensable to realize large-scale renewable energy sources, and to avoid severe power quality problems when they are interconnected into the grid. A battery energy storage system (BESS), combining batteries with a power converter and digital control, should be installed in the vicinity of an intermittent energy source. The fluctuating power is compensated by appropriately controlling an active power stored in, or released from, the battery. This paper describes a 6.6-kV transformerless battery energy storage system based on a cascade multilevel PWM (pulse-width-modulation) converter, with focus on a control method for active power and SOC (state-of-charge) balancing. A down-scaled 200-V, 10-kW, 3.6-kWh (13-MJ) laboratory model using nine NiMH (Nickel Metal Hydride) battery packs is designed, constructed, and tested to verify the viability and effectiveness of the 6.6-kV system.
In the position sensorless vector control of IPMSM, the high frequency signals are usually applied at low speed. However, the application of the high frequency signals will cause noise. The decrease of the noise is required in the railways usage. Therefore, the development of the method without the impression of the high frequency signals that even low speed can carry out the accurate estimation of the rotor position and the rotational speed is demanded. This paper proposes the position sensorless vector control method of IPMSM with the following feature. “Even at low speed, the influence of the stator resistance variation isn't received easily because the proposed method has the stator resistance estimation function.” The success of the proposed method is demonstrated by experiments.
A direct methanol fuel cell (DMFC) is especially expected as a new, high density energy source for mobile usage; however its power density weakness becomes problematic. As a result, the size of a portable electronic equipment using DMFC is far larger than that of the one which uses another battery. Additionally, steady power supply control is difficult, because output power of the DMFC is changed by the environment etc. First of all, this paper presents pulse charge control system that is a new control system applied to a mobile device, which uses the DMFC and an electric double layer capacitor (EDLC), and shows the new passive heat control and the experiment result.
This paper presents a general purpose engine speed control system with an electronic governor in order to improve the current system with a mechanical governor which shows unstable characteristics by change of mecanical friction or A/F ratio (Air/Fuel ratio). For the control system above, there are problems that the feedback signal is only a crank angle because of cost and the controlled object is a general purpose engine which is strongly nonlinear. In order to overcome these problems, the system model is shown for the dynamic estimation of the amount of air flow and the robust controller is designed. That is, the proposed system includes the robust sliding-mode controller by the feedback signal of only a crank angle where Genetic Algorithm is applied for the controller design. The simulation and the experiments by MATLAB/Simulink are performed to show the effectiveness of our proposal.
This paper proposes a dc-voltage equalizing circuit for a diode-clamped linear amplifier (DCLA). The DCLA consists of series-connected complementary MOSFETs and diode clamping circuits, which has an experimental efficiency as high as 90% without switching operation. The DCLA requires a dc-voltage equalizing circuit to divide the dc voltage into several levels. The proposed dc-voltage equalizing circuit enables to use a diode rectifier with a smoothing capacitor as a power supply for the DCLA. Moreover, zero-sequence voltage control is proposed to improve efficiency of the DCLA. As a result, a prototype twelve-series DCLA demonstrates an experimental efficiency as high as 94.7%.
In this paper, a new salient-pole synchronous generator (SG) termed the PMa-SG is presented. In the PMa-SG, permanent magnets (PMs) are placed between the pole shoes to reduce the magnetic saturation in the field poles. By using finite element analysis (FEA), the internal magnetic fields and basic characteristics of a 2.8-MVA PMa-SG were compared with those of a conventional SG of the same size, and the reduction effect of the magnetic saturation of the PMs was examined. The FEA simulations were also validated by experiments on a 2.0-kVA prototype machine. The PMs placed between the pole shoes reduce the magnetic saturation in the pole bodies and pole tips and effectively increase the terminal voltage and output power.
This paper gives a new analysis for efficient drive of synchronous reluctance motors with core loss. The optimal current trajectory that minimizes totally copper and iron losses is newly and analytically derived. And it is shown that the optimal trajectory is a straight line tilting to q-axis with the speed.