Interest has been shown in the concept of an energy storage system aimed at leveling load and improving energy efficiency by charging during vehicle regeneration and discharging during running. Such a system represents an efficient countermeasure against pantograph point voltage drop, power load fluctuation and regenerative power loss. We selected an EDLC model as an energy storage medium and a step-up/step-down chopper as a power converter to exchange power between the storage medium and overhead lines. Basic verification was conducted using a mini-model for DC 400V, demonstrating characteristics suitable for its use as an energy storage system. Based on these results, an energy storage system was built for DC 600V and a verification test conducted in conjunction with the Enoshima Electric Railway Co. Ltd. This paper gives its experimental analysis of voltage drop compensation in a DC electrified railway and some discussions based on the test.
The flash welding is characterized by the high quality, the high production efficiency and the large sectional area welding, and is used to weld rails and hot coils in shop welding mainly. In order to realize high accuracy and high response control of flash welding, the inverter technology has been applied to flash welding in this study. In this paper, a method of process control combined with inverter flash control and mechanical control is proposed. Experiment results of the proposed process control combined with inverter flash control and mechanical control are presented.
This paper describes the study results of the inverters running in parallel. In the consideration of the operation algorithm, it is important to reveal output impedance characteristics of the inverters. First, simulation results demonstrate that the output impedance depends on the control scheme of the output voltage and characteristics of the circulating current that flows through the inverter differs. Next, as examples, two control schemes and their experimental results are demonstrated. The two schemes are: “PQ droop method” based control and “common current distribution method” based control. In the both case, since the output impedance is resistive, the phase of the output voltage is adjusted by using the reactive component of the circulating current. The amplitude of the output voltage is not manipulated. In the latter control system, quantity of the output-current feedback changes with the output impedance. This characteristic clarifies that the output impedance among the inverters becomes higher and the output impedance of the loads gets smaller. Moreover, suppression of the circulating current and excellent output voltage characteristics can be maintained.
In this paper, multirate perfect tracking control is proposed for a single-phase inverter. Although conventional single-rate deadbeat control could not guarantee zero tracking error for arbitrary reference signals, the proposed multirate control can achieve perfect tracking at every sampling point. Feedback characteristic is enhanced by inter sampling technique. Simulations and experiments are carried out to compare the proposed method with a single-rate deadbeat controller for non-sinusoidal reference waveform.
It is necessary to consider variations of circuit element values for power electronic converter design to satisfy a given specification for a frequency characteristic or a dynamic transient response because the variations of element values generate those of the designed characteristic. Therefore element values and their variation ranges should be designed to give a satisfactory characteristic within an allowable specification range or a tolerance. This analysis is so-called tolerance or worst-case analysis. The analysis is a sort of nonlinear minimum and maximum (min/max) problem with respect to circuit or system parameters. However it is not possible to solve a transient type problem generally. Hence, the problem is converted to a simpler and easier one with various techniques. This paper proposes a new Genetic Algorithm (GA) method, or a sort of a modified relay-search-GA, which is suitable for practical and efficient tolerance analysis by considering diversity of solutions. Output voltage analysis examples of three types of converters for element parameter variations are investigated for effectiveness of the proposed method.
This paper proposes a speed and position estimation methods by using a Hall effect sensor. The speed is estimated from the fluctuated current which can be observed on the control axis. The position is estimated from the estimated speed and is corrected from the pulse which is generated by the Hall effect sensor mounted on the machine. Although the speed control range is limitted since this method is based on the back EMF, the speed and the position can be estimated without any motor parameter is used. The prposed method is verified by the experiments which 120W SPMSM is used for the tested machine, the currnet control and the speed control results including the controlable speed range are breifly explained.
The double null-flux electro-dynamic suspension (EDS) in the superconducting maglev has the coupling lateral and yawing stiffness, which does not coincide with each other, so special attention should be paid to the dynamic stability of lateral and yawing motions. This paper describes their intrinsic dynamic stability by analyzing the lateral and yawing motions of bogie levitated by the double null-flux EDS.
This paper describes a novel safety driving control scheme for electric power assisted wheelchairs based on the regenerative braking system. “Electric power assisted wheelchair” which assists the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people, however, the safe and secure driving performance especially on downhill roads must be further improved because electric power assisted wheelchairs have no braking devices. The proposed control system automatically switches the driving mode, from “assisting mode” to “braking mode”, based on the wheelchair's velocity and the declined angle and smoothly suppresses the wheelchair's acceleration based on variable duty ratio control in order to realize the safety driving and to improve the ride quality. Some experiments on the practical roads and subjective evaluation show the effectiveness of the proposed control system.
This paper proposes a novel control method for the active power quality compensator used in electrified railways. In the proposed method, only the constant dc voltage control is used to compensate the non-active and unbalanced active currents on the secondary side of the Scott transformer. Any schemes to detect the reactive and harmonic currents are not needed. Thus we can provide the simplest way to improve the power quality in electrified railways. The basic principle of the proposed control method is discussed. The validity and excellent practicability are confirmed by digital computer simulation using PSIM soft ware.
An improvement in the input current distortion of single-phase two-stage boost rectifier is studied. To cause the input current to follow its sinusoidal reference by means of current-mode control, a capacitor voltage is superimposed upon that of the supply when the switches are turned on. The experimental prototype, employing two insulated-gate bipolar transistors as active power switching devices and PI controller for output voltage regulation, is implemented to investigate the operation. The experimental results confirm that the input current can be waveshaped sinusoidally with a near-unity power factor independent of the working conditions.
Combined-levitation-and-propulsion single-sided linear induction motor (SLIM) vehicle can be levitated without any additional levitation system. When the vehicle runs, the attractive-normal force varies depending on the phase of primary current because of the short primary end effect. The ripple of the attractive-normal force causes the vertical vibration of the vehicle. In this paper, instantaneous attractive-normal force is analyzed by using space harmonic analysis method. And based on the analysis, vertical vibration control is proposed. The validity of the proposed control method is verified by numerical simulation.
A novel single-phase voltage-doubler rectifier using the parallel charge-pump circuit is presented. This is based on a diode charge pump circuit which is composed of only passive devices without switching devices. Using this rectifier, the harmonic components in the supply current are reduced and the power factor is improved. The validity is demonstrated by the simulation and experimental implementations.