In recent year, consciousness of environmental problems is enhancing, and the price of the electric power purchased by an electric power company is established expensive for the power plant utilizing the natural energy. So, the introduction of the wind power generation is promoted in Japan. Generally, squirrel-cage induction machines are widely used as a generator in wind power generation system because of its small size, lightweight and low-cost. However, the induction machines do not have a source of excitation. Thus, it causes the inrush currents and the instantaneous voltage drop when the generator is directly connected to a power grid. To reduce the inrush currents, an AC power regulator is used. Wind power generations are frequently connected to and disconnected from the power grid. However, when the inrush currents are reduced, harmonic currents are caused by phase control of the AC power regulator. And the phase control of AC power regulator cannot control the power factor. Therefore, we propose the use of the AC power regulator to compensate for the harmonic currents and reactive power in the wind power generation system, and demonstrate the validity of its system by simulated and experimental results.
This paper presents a new maximum power point tracking control for photovoltaic (PV) panels. The control can be categorized into the Perturb and Observe (P & O) method. It utilizes instantaneous voltage ripples at PV panel output terminals caused by the switching of a chopper connected to the panel in order to identify the direction for the maximum power point (MPP). The tracking for the MPP is achieved by a feedback control of the average terminal voltage of the panel. Appropriate use of the instantaneous and the average values of the PV voltage for the separate purposes enables both the quick transient response and the good convergence with almost no ripples simultaneously. The tracking capability is verified experimentally with a 2.8 W PV panel under a controlled experimental setup. A numerical comparison with a conventional P & O confirms that the proposed control extracts much more power from the PV panel.
Generally, PMSM is driven by the vector control based on the current control. However, in spite of using the vector control, there are harmonic components in the current control loop of vector control system due to several causes. Authors have proposed the suppression control method of harmonic current in the vector control system for PMSM using the repetitive control with Fourier Transform. The proposed control method, however, was carried out individually for each harmonic current component with Fourier Transform and phase adjustment of compensational signals to stabilize the system, so that the process of learning compensation signal was complicated and required much calculation time on the DSP. In this paper, we propose a new control method suppressing all harmonic current components simultaneously without Fourier Transform and phase adjustment of compensational signal. Although, in theoretical, the repetitive control is useful on the steady state, our proposed method is applied to a motor drive system which has a transient state frequently. Therefore, considering the stability on the transient state of the motor and faster harmonics convergence after motor speed changed, it is desirable that the stability margin of the control system keeps larger and relearning speed of compensational signal is faster. In this paper, we additionally propose a method improving the stability margin of the control system and the convergence speed of harmonics. By the stability analysis of experimental results, we confirm the new proposed control method.
This paper proposes a new robust feedforward tracking servo system for optical disk recording system with considering a sudden disturbance for optical disk recording system. In optical recording systems, the tracking servo system must suppress tracking error below its tolerance. This paper designs the robust feedback control system by using the coprime factorization and disturbance observer. The proposed robust feedback control system suppresses the sudden disturbance caused by walking and running. The detecting signal of optical disk recording system is only a tracking error. Hence, the feedforward controller of the proposed tracking control system is constructed based on both “Zero Phase Error Tracking" (ZPET) control theory and prediction of tracking error. The experimental results point out that the proposed tracking servo system has a quick and precise tracking response and keeps the residual tracking error below its tolerance.
This paper presents a novel on-line parameter identification method for sensorless control of Synchronous Reluctance Motors (SynRMs). Although conventional sensorless control methods based on mathematical models usually need some complex measurements of motor parameters in advance, the proposed identification method does not require them and can be realized on-line. The proposed method identifies motor parameters under sensorless control, so rotor position and velocity can not be used to identify these parameters. However, the proposed method does not need rotor position and veocity, identified parameters are not affected by these estimation errors. The sensorless control using identified motor parameters is realized, and effective of the proposed method is verified by experimental results.
This paper describes a method of servo-drive system selection for a mechatronic servo system configuration. A conventional selection guide does not consider a control performance of mechatronic servo system in any selection phase, but it only considers driving torque and maximum speed. The proposed selection method is derived by taking into account of torque saturation of power amplifier. Effectiveness of the proposed selection method is assured by experiment and actual selection.
In previous papers, we proposed the Cylindrical Rotor Type Switched Reluctance Motor (SRM), in which q-axis short-circuited windings were wound around the q-axis iron poles of the rotor and the stator windings were excited by the usual pulse current. It is confirmed experimentally that the short-circuited windings reduced the q-axis leakage flux and caused additional torque generation. In this paper we describe characteristic analysis of the new type SRM using the circuit simulation considering all the inductances coupled with the FEM analysis.
The topology optimization using the density method, which determines the optimal topology by distributing the magnetic material in the design domain, is attractive for designers of magnetic devices, because an initial conceptual design can be obtained. As the number of design variables in design domain is so huge, a sufficient solution cannot be obtained by using the direct search method. Then, the steepest descent method is adopted to obtain the fast convergence. In this paper, some problems in applying the density method to the practical topology optimization are investigated. The accuracy of calculating the sensitivity using the adjoint variables method and the effect of initial material density on the obtained results are examined. The effectiveness of the proposed optimization method is illustrated by applying it to the determination of the optimal topology of permanent magnet which generates a uniform magnetic field.
This paper describes direct power control of a neutral-point-clamped PWM converter. The key of this strategy is a direct selection of switching modes on the basis of instantaneous control errors of active and reactive power. In addition, this paper discusses neutral point voltage control and PWM pattern equalization schemes. The validity of the proposed technique was examined by computer simulations and experiments after theoretical analyses. Through several experimental tests, it was confirmed that total input power factor and efficiency were more than 99% and 97% over the load power range from 400 to 2000W, respectively. The experimental results demonstrated excellent performance of the proposed method, compared with a conventional control technique of the neutral-point-clamped PWM converter.
This paper presents a three-phase PWM current source inverter-induction motor drive system with photovoltaic generation. The system is interacted to single-phase utility using PWM converter, and the photovoltaic arrays are connected to the dc link of the system by employing a step-down chopper. The chopper is operated on PWM switching, and contributes to maintain the maximum power of the arrays and to smooth the dc link current in the small dc reactor. The PWM converter can flow the power in bidirection between the system and the utility with a sinusoidal current in the ac side. In this paper, the system configuration and the control methods are shown. First of all, the PWM strategy of the chopper, which depends on the converter PWM operation, is explained in detail and the switching patterns are given. Next, the experimental and the theoretical results at the steady state operations are given, and it is shown that the use of the PWM chopper is effective for the improvement of the ac waveforms. Finally, the waveforms at the transient operation are given in the variable speed drive of the motor and the change of the sunlight quantity for the arrays. The results prove that the proposed system has good performances for the utilization of the photovoltaic power.
A novel simulation model for multiphase induction machines formulated by the modified nodal analysis is proposed. In the proposed model, the voltage and the torque equations for an elementary induction machine are used to formulate a multiphase induction machine. It is not necessary to derive the state equations for the multiphase induction machine corresponding to the conduction modes of a power electronics circuit. Thus, it is easy to simulate the complex systems including the multiphase induction machines and many power devices. Two brushless slip-power recovery systems are discussed in this paper to verify the effectiveness of the proposed model. The simulation results show good agreements with the experimental results. The proposed model enables to simulate the systems consisting of the multiphase induction machines and many power devices without derivations of the state equations for multiphase induction machines corresponding to the conduction modes of a power electronics circuit.
In the superconducting maglev vehicle, levitation forces produced by the interaction between the ground levitation coils and the onboard SCMs become insufficient when the running speed is low. This paper presents a levitation force assist method through the control of LSM armature currents, which usually function to generate propulsion forces. The levitation assist system is constructed in terms of d-axis armature currents, leading to the definition of the vertical force coefficient of propulsion system. The calculated results show the feasibility of the system, which produces damping forces as well as assist levitation forces.
This paper introduces a position sensor-less control technique making use of mechanical springs. The principle of the technique is based on achievement of observability. And it is different from other conventional position sensor-less control methods which often use pure integral calculation. And it proves that the presented method fits for practical use on real electro-mechanical systems by showing the experimental results. The implementation making best use of both electrical and mechanical characteristics show us the essence of motion control technique because of its good performance.
The permanent-magnet induction generator (PMIG) is a new type of induction machine that has a permanent-magnet rotor inside a squirrel-cage rotor. In this paper, a new technique for the magnetic field analysis of the PMIG is proposed. The proposed technique is based on the PMIG's equivalent circuit and the two-dimensional finite-element analysis (2D-FEA). To execute the 2D-FEA, the phasors of primary and secondary currents are calculated from the equivalent circuit, and the input data for the 2D-FEA is found by converting these phasors into the space vectors. As a result, the internal magnetic fields of the PMIG can be easily analyzed without complicated calculations.
In conveyance systems as crane, both a control mode based on operator's command and an automatic control mode are required. Taking the feature of the nonstationary optimal control method (NOCM) into account, this study applies the idea of NOCM to the problem consisting of the traveling control mode following the operator's command and the automatic settling control mode for positioning of a cart with vibration system. The effectiveness of the method is verified experimentally.
FEM is well known as a powerful tool for the analysis of electromagnetic field in electromagnetic devices. MATLAB/Simulink is also well known as a very useful tool for the analysis and design of control systems. This paper proposes a new method, where the MATLAB/Simulink is coupled with FEM. We apply the proposed method to analyze the permanent magnet motor drive system, and show that it can take into consideration the torque ripple and space harmonics of the motor, which are not considered in MATLAB/Simulink. The computational time is reasonable in the case where the non-linearity is not significant.